Specialized integrated light source using a laser diode

ABSTRACT

The present invention provides a device and method for an integrated white colored electromagnetic radiation source using a combination of laser diode excitation sources based on gallium and nitrogen containing materials and light emitting source based on phosphor materials. In this invention a violet, blue, or other wavelength laser diode source based on gallium and nitrogen materials is closely integrated with phosphor materials, such as yellow phosphors, to form a compact, high-brightness, and highly-efficient, white light source.

BACKGROUND OF THE INVENTION

In the late 1800's, Thomas Edison invented the light bulb. Theconventional light bulb, commonly called the “Edison bulb,” has beenused for over one hundred years for a variety of applications includinglighting and displays. The conventional light bulb uses a tungstenfilament enclosed in a glass bulb sealed in a base, which is screwedinto a socket. The socket is coupled to an AC power or DC power source.The conventional light bulb can be found commonly in houses, buildings,and outdoor lightings, and other areas requiring light or displays.Unfortunately, drawbacks exist with the conventional light bulb:

-   -   The conventional light bulb dissipates more than 90% of the        energy used as thermal energy.    -   The conventional light bulb routinely fails due to thermal        expansion and contraction of the filament element.    -   The conventional light bulb emits light over a broad spectrum,        much of which is not perceived by the human eye.    -   The conventional light bulb emits in all directions, which is        undesirable for applications requiring strong directionality or        focus, e.g. projection displays, optical data storage, etc.

To overcome some of the drawbacks of the conventional light bulb,fluorescent lighting has been developed. Fluorescent lighting uses anoptically clear tube structure filled with a halogen gas and, whichtypically also contains mercury. A pair of electrodes is coupled betweenthe halogen gas and couples to an alternating power source through aballast. Once the gas has been excited, it discharges to emit light.Typically, the optically clear tube is coated with phosphors, which areexcited by the light. Many building structures use fluorescent lightingand, more recently, fluorescent lighting has been fitted onto a basestructure, which couples into a standard socket.

Due to the high efficiency, long lifetimes, low cost, and non-toxicityoffered by solid state lighting technology, light emitting diodes (LED)have rapidly emerged as the illumination technology of choice. An LED isa two-lead semiconductor light source typically based on a p-i-njunction diode, which emits electromagnetic radiation when activated.The emission from an LED is spontaneous and is typically in a Lambertianpattern. When a suitable voltage is applied to the leads, electrons andholes recombine within the device releasing energy in the form ofphotons. This effect is called electroluminescence, and the color of thelight is determined by the energy band gap of the semiconductor.

Appearing as practical electronic components in 1962 the earliest LEDsemitted low-intensity infrared light. Infrared LEDs are still frequentlyused as transmitting elements in remote-control circuits, such as thosein remote controls for a wide variety of consumer electronics. The firstvisible-light LEDs were also of low intensity, and limited to red.Modern LEDs are available across the visible, ultraviolet, and infraredwavelengths, with very high brightness.

The earliest blue and violet gallium nitride (GaN)-based LEDs werefabricated using a metal-insulator-semiconductor structure due to a lackof p-type GaN. The first p-n junction GaN LED was demonstrated by Amanoet al. using the LEEBI treatment to obtain p-type GaN in 1989. Theyobtained the current-voltage (I-V) curve and electroluminescence of theLEDs, but did not record the output power or the efficiency of the LEDs.Nakamura et al. demonstrated the p-n junction GaN LED using thelow-temperature GaN buffer and the LEEBI treatment in 1991 with anoutput power of 42 uW at 20 mA. The first p-GaN/n-InGaN/n-GaN DH blueLEDs were demonstrated by Nakamura et al. in 1993. The LED showed astrong band-edge emission of InGaN in a blue wavelength regime with anemission wavelength of 440 nm under a forward biased condition. Theoutput power and the EQE were 125 uW and 0.22%, respectively, at aforward current of 20 mA. In 1994, Nakamura et al. demonstratedcommercially available blue LEDs with an output power of 1.5 mW, an EQEof 2.7%, and the emission wavelength of 450 nm. On Oct. 7, 2014, theNobel Prize in Physics was awarded to Isamu Akasaki, Hiroshi Amano andShuji Nakamura for “the invention of efficient blue light-emittingdiodes which has enabled bright and energy-saving white light sources”or, less formally, LED lamps.

By combining GaN-based LEDs with wavelength converting materials such asphosphors, solid-state white light sources were realized. Thistechnology utilizing GaN-based LEDs and phosphor materials to producewhite light is now illuminating the world around us as a result of themany advantages over incandescent light sources including lower energyconsumption, longer lifetime, improved physical robustness, smallersize, and faster switching. Light-emitting diodes are now used inapplications as diverse as aviation lighting, automotive headlamps,advertising, general lighting, traffic signals, and camera flashes. LEDshave allowed new text, video displays, and sensors to be developed,while their high switching rates are also useful in advancedcommunications technology.

Although useful, LEDs still have limitations that are desirable toovercome in accordance to the inventions described in the followingdisclosure.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a device and method for an integratedwhite colored electromagnetic radiation source using a combination oflaser diode excitation sources based on gallium and nitrogen containingmaterials and light emitting source based on phosphor materials. In thisinvention a violet, blue, or other wavelength laser diode source basedon gallium and nitrogen materials is closely integrated with phosphormaterials, such as yellow phosphors, to form a compact, high-brightness,and highly-efficient, white light source. In an example, the source canbe provided for specialized applications, among general applications,and the like.

Additional benefits are achieved over pre-existing techniques using thepresent invention. In particular, the present invention enables acost-effective white light source. In a specific embodiment, the presentoptical device can be manufactured in a relatively simple and costeffective manner. Depending upon the embodiment, the present apparatusand method can be manufactured using conventional materials and/ormethods according to one of ordinary skill in the art. In someembodiments of this invention the gallium and nitrogen containing laserdiode source is based on c-plane gallium nitride material and in otherembodiments the laser diode is based on nonpolar or semipolar galliumand nitride material. In one embodiment the white source is configuredfrom a chip on submount (CoS) with an integrated phosphor on thesubmount to form a chip and phosphor on submount (CPoS) white lightsource.

In various embodiments, the laser device and phosphor device are mountedon a common support member with or without intermediate submounts andthe phosphor materials are operated in a transmissive mode or areflective mode to result in a white emitting laser-based light source.Merely by way of example, the invention can be applied to applicationssuch as white lighting, white spot lighting, flash lights, automobileheadlights, all-terrain vehicle lighting, light sources used inrecreational sports such as biking, surfing, running, racing, boating,light sources used for drones, planes, robots, other mobile or roboticapplications, safety, counter measures in defense applications,multi-colored lighting, lighting for flat panels, medical, metrology,beam projectors and other displays, high intensity lamps, spectroscopy,entertainment, theater, music, and concerts, analysis fraud detectionand/or authenticating, tools, water treatment, laser dazzlers,targeting, communications, transformations, transportations, leveling,curing and other chemical treatments, heating, cutting and/or ablating,pumping other optical devices, other optoelectronic devices and relatedapplications, and source lighting and the like.

Laser diodes are ideal as phosphor excitation sources. With a spatialbrightness (optical intensity per unit area) more than 10,000 timeshigher than conventional LEDs, extreme directionality of the laseremission, and without the droop phenomenon that plagues LEDs, laserdiodes enable characteristics unachievable by LEDs and other lightsources. Specifically, since the laser diodes output beams carrying over1 W, over 5 W, over 10 W, or even over 100 W can be focused to verysmall spot sizes of less than 1 mm in diameter, less than 500 microns indiameter, less than 100 microns in diameter, or even less than 50microns in diameter, power densities of over 1 W/mm2, 100 W/mm2, or evenover 2,500 W/mm2 can be achieved. When this very small and powerful beamof laser excitation light is incident on a phosphor material anextremely bright spot or point source of white light can be achieved.Assuming a phosphor conversion ratio of 200 lumens of emitted whitelight per optical watt of excitation light, a 5 W excitation power couldgenerate 1000 lumens in a beam diameter of 100 microns, or 50 microns,or less. This unprecedented source brightness can be game changing inapplications such as spotlighting or range finding where parabolicreflectors or lensing optics can be combined with the point source tocreate highly collimated white light spots that can travel drasticallyhigher distances than ever possible before using LEDs or bulbtechnology.

In one embodiment, the present invention provides a CPoS laser-basedwhite light source comprising a form factor characterized by a length, awidth, and a height. In an example, the height is characterized by adimension of less than 25 mm, and greater than 0.5 mm, although theremay be variations. In an alternative example, the height ischaracterized by a dimension of less than 12.5 mm, and greater than 0.5mm, although there may be variations. In yet an alternative example, thelength and width are characterized by a dimension of less than 30 mm,less than 15 mm, or less than 5 mm, although there may be variations.The apparatus has a support member and at least one gallium and nitrogencontaining laser diode devices and phosphor material overlying thesupport member. The laser device is capable of an emission of a laserbeam with a wavelength preferably in the blue region of 425 nm to 475 nmor in the ultra violet or violet region of 380 nm to 425 nm, but can beother such as in the cyan region of 475 nm to 510 nm or the green regionof 510 nm to 560 nm. In a preferred embodiment the phosphor material canprovide a yellowish emission in the 550 nm to 590 nm range such thatwhen mixed with the blue emission of the laser diode a white light isproduced. In other embodiments phosphors with red, green, yellow, andeven blue emission can be used in combination with the laser diodeexcitation source to produce a white light with color mixing.

The apparatus typically has a free space with a non-guided laser beamcharacteristic transmitting the emission of the laser beam from thelaser device to the phosphor material. The laser beam spectral width,wavelength, size, shape, intensity, and polarization are configured toexcite the phosphor material. The beam can be configured by positioningit at the precise distance from the phosphor to exploit the beamdivergence properties of the laser diode and achieve the desired spotsize. In one embodiment, the incident angle from the laser to thephosphor is optimized to achieve a desired beam shape on the phosphor.For example, due to the asymmetry of the laser aperture and thedifferent divergent angles on the fast and slow axis of the beam thespot on the phosphor produced from a laser that is configured normal tothe phosphor would be elliptical in shape, typically with the fast axisdiameter being larger than the slow axis diameter. To compensate this,the laser beam incident angle on the phosphor can be optimized tostretch the beam in the slow axis direction such that the beam is morecircular on phosphor. In other embodiments free space optics such ascollimating lenses can be used to shape the beam prior to incidence onthe phosphor. The beam can be characterized by a polarization purity ofgreater than 50% and less than 100%. As used herein, the term“polarization purity” means greater than 50% of the emittedelectromagnetic radiation is in a substantially similar polarizationstate such as the transverse electric (TE) or transverse magnetic (TM)polarization states, but can have other meanings consistent withordinary meaning. In an example, the laser beam incident on the phosphorhas a power of less than 0.1 W, greater than 0.1 W, greater than 0.5 W,greater than 1 W, greater than 5 W, greater than 10 W, or greater than20 W.

The phosphor material can be operated in a transmissive mode, areflective mode, or a combination of a transmissive mode and reflectivemode, or other modes. The phosphor material is characterized by aconversion efficiency, a resistance to thermal damage, a resistance tooptical damage, a thermal quenching characteristic, a porosity toscatter excitation light, and a thermal conductivity. The phosphor mayhave an intentionally roughened surface to increase the light extractionfrom the phosphor. In a preferred embodiment the phosphor material iscomprised of a yellow emitting YAG material doped with Ce with aconversion efficiency of greater than 100 lumens per optical watt,greater than 200 lumens per optical watt, or greater than 300 lumens peroptical watt, and can be a polycrystalline ceramic material or a singlecrystal material. The white light apparatus also has an electrical inputinterface configured to couple electrical input power to the laser diodedevice to generate the laser beam and excite the phosphor material. Thewhite light source configured to produce greater than 1 lumen, 10lumens, 100 lumens, 1000 lumens, or greater of white light output. Thesupport member is configured to transport thermal energy from the atleast one laser diode device and the phosphor material to a heat sink.The support member is configured to provide thermal impedance of lessthan 10 degrees Celsius per watt or less than 5 degrees Celsius per wattof dissipated power characterizing a thermal path from the laser deviceto a heat sink. The support member is comprised of a thermallyconductive material such as copper, copper tungsten, aluminum, SiC,sapphire, AlN, or other metals, ceramics, or semiconductors.

In a preferred configuration of this integrated white light source, thecommon support member comprises the same submount that the gallium andnitrogen containing laser diode chip is directly bonded to. That is, thelaser diode chip is mounted down or attached to a submount configuredfrom a material such as SiC, AlN, or diamond and the phosphor materialis also mounted to this submount, such that the submount is the commonsupport member. The phosphor material may have an intermediate materialpositioned between the submount and the phosphor. The intermediatematerial may be comprised of a thermally conductive material such ascopper. The laser diode can be attached to a first surface of thesubmount using conventional die attaching techniques using solders suchas AuSn solder, SAC solder, lead containing solder, or indium, but canbe others. Similarly, the phosphor material may be bonded to thesubmount using a soldering technique, but it can be other techniquessuch as gluing technique or epoxy technique. Optimizing the bond for thelowest thermal impedance is a key parameter for heat dissipation fromthe phosphor, which is critical to prevent phosphor degradation andthermal quenching of the phosphor material.

In an alternative configuration of this white light source, the laserdiode is bonded to an intermediate submount configured between thegallium and nitrogen containing laser chip and the common supportmember. In this configuration, the intermediate submount can becomprised of SiC, AlN, diamond, or other, and the laser can be attachedto a first surface of the submount using conventional die attachingtechniques using solders such as AuSn solder, but can be othertechniques such as. The second surface of the submount can be attachedto the common support member using similar techniques, but could beothers. Similarly, the phosphor material may have an intermediatematerial or submount positioned between the common support member andthe phosphor. The intermediate material may be comprised of a thermallyconductive material such as copper. The phosphor material may be bondedusing a soldering technique. In this configuration, the common supportmember should be configured of a thermally conductive material such ascopper or copper tungsten. Optimizing the bond for the lowest thermalimpedance is a key parameter for heat dissipation from the phosphor,which is critical to prevent phosphor degradation and thermal quenchingof the phosphor material.

In yet another preferred variation of this CPoS integrated white lightsource, a process for lifting-off gallium and nitrogen containingepitaxial material and transferring it to the common support member canbe used to attach the gallium and nitrogen containing laser epitaxialmaterial to a submount member. In this embodiment, the gallium andnitrogen epitaxial material is released from the gallium and nitrogencontaining substrate it was epitaxially grown on. As an example, theepitaxial material can be released using a photoelectrochemical (PEC)etching technique. It is then transferred to a submount material usingtechniques such as wafer bonding wherein a bond interface is formed. Forexample, the bond interface can be comprised of a Au—Au bond. Thesubmount material preferably has a high thermal conductivity such asSiC, wherein the epitaxial material is subsequently processed to form alaser diode with a cavity member, front and back facets, and electricalcontacts for injecting current. After laser fabrication is complete, aphosphor material is introduced onto the submount to form an integratedwhite light source. The phosphor material may have an intermediatematerial positioned between the submount and the phosphor. Theintermediate material may be comprised of a thermally conductivematerial such as copper. The phosphor material can be attached to to thesubmount using conventional die attaching techniques using solders suchas AuSn solder, SAC solder, lead containing solder, or indium, but canbe others. Optimizing the bond for the lowest thermal impedance is a keyparameter for heat dissipation from the phosphor, which is critical toprevent phosphor degradation and thermal quenching of the phosphormaterial. The benefits of using this embodiment with lifted-off andtransferred gallium and nitrogen containing material are the reducedcost, improved laser performance, and higher degree of flexibility forintegration using this technology.

In all embodiments of this integrated white light source, the presentinvention may include safety features and design considerations. In anybased laser based source, safety is a key aspect. It is critical thatthe light source cannot be compromised or modified in such a way tocreate laser diode beam that can be harmful to human beings, animals, orthe environment. Thus, the overall design should include safetyconsiderations and features, and in some cases even active componentsfor monitoring. Examples of design considerations and features forsafety include positioning the laser beam with respect to the phosphorin a way such that if the phosphor is removed or damaged, the exposedlaser beam would not make it to the outside environment in a harmfulform such as collimated, coherent beam. More specifically, the whitelight source is designed such that laser beam is pointing away from theoutside environment and toward a surface or feature that will preventthe beam from being reflected to the outside world. In an example of apassive design features for safety include beam dumps and/or absorbingmaterial can be specifically positioned in the location the laser beamwould hit in the event of a removed or damaged phosphor.

In some embodiments of this invention, safety features and systems useactive components. Example active components includephotodiodes/photodetectors and thermistors. Strategically locateddetectors designed to detect direct blue emission from the laser,scatter blue emission, or phosphor emission such as yellow phosphoremission can be used to detect failures of the phosphor where a bluebeam could be exposed. Upon detection of such an event, a close circuitor feedback loop would be configured to cease power supply to the laserdiode and effectively turn it off. As an example, a detector used todetect phosphor emission could be used to determine if the phosphoremission rapidly reduced, which would indicate that the laser is nolonger effectively hitting the phosphor for excitation and could meanthat the phosphor was removed or damaged. In another example of activesafety features, a blue sensitive photodetector could be positioned todetect reflected or scatter blue emission from the laser diode such thatif the phosphor was removed or compromised the amount of blue lightdetected would rapidly increase and the laser would be shut off by thesafety system. In yet another example of active safety features athermistor could be positioned near or under the phosphor material todetermine if there was a sudden increase in temperature which may be aresult of increased direct irradiation from the blue laser diodeindicating a compromised or removed phosphor. Again, in this case thethermistor signal would trip the feedback loop to cease electrical powerto the laser diode and shut it off. Of course these are merely exampleembodiments, there are several configurations for photodiodes and/orthermistors to be integrated with a laser based white light source toform a safety feature such as a feedback loop to cease operation of thelaser.

In all embodiments of the integrated white light source final packagingwould need to be considered. There are many aspects of the package thatshould be accounted for such as form factor, cost, functionality,thermal impedance, sealing characteristics, and basic compatibility withthe application. Form factor will depend on the application, but ingeneral making the smallest size packaged white source will bedesirable. Cost should be minimized in all applications, but in someapplications cost will be the most important consideration. In suchcases using an off-the-shelf packages produced in high volume may bedesirable. Functionality options include direction and properties of theexiting light emission for the application as well as integration offeatures such as photodetectors, thermistors, or other electronics oropolectronics. For best performance and lifetime the thermal impedanceof the package should be minimized, especially in high powerapplications. Examples of sealing configurations include openenvironment, environmentally sealed, or hermetically sealed. Typicallyfor GaN based lasers it is desirable for hermetically sealed packages,but other packages can be considered and deployed for variousapplications. Examples of off the shelf packages for the integratedwhite light source include TO cans such as TO38, TO56, TO9, TO5, orother TO can type packages. Flat packages configured with windows canalso be used. Examples of flat packages include a butterfly package likea TOSA. Surface mount device (SMD) packages can also be used, which areattractive due to their low price, hermetic sealing, and potentially lowthermal impedance. In other embodiments, custom packages are used.

In some embodiments of this invention, the integrated white light sourceis combined with one or more optical members to manipulate the generatedwhite light. In an example the white light source could serve in a spotlight system such as a flashlight or an automobile headlamp or otherlight applications where the light must be directed or projected to aspecified location or area. In one embodiment a reflector is coupled tothe white light source. Specifically, a parabolic (or paraboloid orparaboloidal) reflector is deployed to project the white light. Bypositioning the white light source in the focus of a parabolicreflector, the plane waves will be reflected and propagate as acollimated beam along the axis of the parabolic reflector. In an anotherexample a lens is used to collimate the white light into a projectedbeam. In one example a simple aspheric lens would be positioned in frontof the phosphor to collimate the white light. In other embodiments othertypes of collimating optics may be used such as spherical lenses oraspherical lenses.

In a specific embodiment of the general invention described above, thepresent invention is configured for a side-pumped phosphor operated intransmissive mode. In this configuration, the phosphor is positioned infront of the laser facet outputting the laser beam, wherein both thelaser and the phosphor are configured on a support member. The galliumand nitrogen containing laser diode is configured with a cavity that hasa length greater than 100 um, greater than 500 um, greater than 1000 um,or greater than 1500 um long and a width greater than 1 um, greater than10 um, greater than 20 um, greater than 30 um, or greater than 45 um.The cavity is configured with a front facets and back facet on the endwherein the front facet comprises the output facet and emits the laserbeam incident on the phosphor. The output facet may contain an opticalcoating to reduce the reflectivity in the cavity. The back facet can becoated with a high reflectivity coating to reduce the amount of lightexiting the back of the laser diode. The phosphor is comprised of Cedoped YAG and emits yellow emission. The phosphor is shaped as a block,plate, sphere, cylinder, or other geometrical form. Specifically, thephosphor geometry primary dimensions may be less than 50 um, less than100 um, less than 200 um, less than 500 um, less than 1 mm, or less than10 mm. Operated in transmissive mode, the phosphor has a first primaryside for receiving the incident laser beam and at least a second primaryside where most of the useful white light will exit the phosphor to becoupled to the application. To improve the efficiency by maximizing theamount of light exiting the second side of the phosphor, the phosphormay be coated with layers configured to modify the reflectivity forcertain colors. In one example, a coating configured to increase thereflectivity for yellow light is applied to the first side of thephosphor such that the amount of yellow light emitted from the firstside is reduce. In an another example, a coating to increase thereflectivity of the blue light is spatially patterned on the first sideof the phosphor to allow the excitation light to pass, but preventbackward propagating scattered light to escape. In another example,optical coatings configured to reduce the reflectivity to yellow andblue light are applied to at least the second side of the phosphor tomaximize the light escaping from this primary side where the usefullight exits. With respect to attaching the phosphor to the commonsupport member, thermal impedance is a key consideration. The thermalimpedance of this attachment joint should be minimized using the bestattaching material, interface geometry, and attachment process practicesfor the lowest thermal impedance with sufficient reflectivity. Examplesinclude AuSn solders, SAC solders, lead containing solders, indiumsolders, indium, and other solders. The joint could also be formed fromthermally conductive glues, thermal epoxies such as silver epoxy,thermal adhesives, and other materials. Alternatively the joint could beformed from a metal-metal bond such as a Au—Au bond. The common supportmember with the laser and phosphor material is configured to providethermal impedance of less than 10 degrees Celsius per watt or less than5 degrees Celsius per watt of dissipated power characterizing a thermalpath from the laser device to a heat sink. The support member iscomprised of a thermally conductive material such as copper, coppertungsten, aluminum, SiC, sapphire, AlN, or other metals, ceramics, orsemiconductors. The side-pumped transmissive apparatus has a form factorcharacterized by a length, a width, and a height. In an example, theheight is characterized by a dimension of less than 25 mm, and greaterthan 0.5 mm, although there may be variations. In an alternativeexample, the height is characterized by a dimension of less than 12.5mm, and greater than 0.5 mm, although there may be variations. In yet analternative example, the length and width are characterized by adimension of less than 30 mm, less than 15 mm, or less than 5 mm,although there may be variations.

In alternative embodiments of the present invention, multiple phosphorsare operated in a transmissive mode for a white emission. In oneexample, a violet laser diode configured to emit a wavelength of 395 nmto 425 nm and excite a first blue phosphor and a second yellow phosphor.In this configuration, a first blue phosphor plate could be fused orbonded to the second yellow phosphor plate. In a practical configurationthe laser beam would be directly incident on the first blue phosphorwherein a fraction of the blue emission would excite the second yellowphosphor to emit yellow emission to combine with blue emission andgenerate a white light. Additionally, the violet pump would essentiallyall be absorbed since what may not be absorbed in the blue phosphorwould then be absorbed in the yellow phosphor. In an alternativepractical configuration the laser beam would be directly incident on thesecond yellow phosphor wherein a fraction of the violet electromagneticemission would be absorbed in the yellow phosphor to excite yellowemission and the remaining violet emission would pass to the bluephosphor and create a blue emission to combine a yellow emission with ablue emission and generate a white light.

In an alternative embodiment of a multi-phosphor transmissive exampleaccording to the present invention, a blue laser diode operating with awavelength of 425 nm to 480 nm is configured to excite a first greenphosphor and a second red phosphor. In this configuration, a first greenphosphor plate could be fused or bonded to the second red phosphorplate. In a practical configuration the laser beam would be directlyincident on the first green phosphor wherein a fraction of the greenemission would excite the second red phosphor to emit red emission tocombine with green phosphor emission and blue laser diode emission togenerate a white light. In an alternative practical configuration thelaser beam would be directly incident on the second red phosphor whereina fraction of the blue electromagnetic emission would be absorbed in thered phosphor to excite red emission and a portion of the remaining bluelaser emission would pass to the green phosphor and create a greenemission to combine with the red phosphor emission and blue laser diodeemission to generate a white light. The benefit or feature of thisembodiment is the higher color quality that could be achieved from awhite light comprised of red, green, and blue emission. Of course therecould be other variants of this invention including integrating morethan two phosphor and could include one of or a combination of a red,green, blue, and yellow phosphor.

In yet another variation of a side pumped phosphor configuration, a“point source” or “point source like” integrated white emitting deviceis achieved. In this configuration the phosphor would most likely have acube geometry or spherical geometry such that white light can be emittedfrom more than 1 primary emission surface. For example, in a cubegeometry up to all six faces of the cube can emit white light or in asphere configuration the entire surface can emit to create a perfectpoint source. In some configurations of this embodiment the phosphor isattached to the common support member wherein the common support membermay not be fully transparent. In this configuration the surface or sideof the phosphor where it is attached would have impeded light emissionand hence would reduce the overall efficiency or quality of the pointsource white light emitter. However, this emission impediment can beminimized or mitigated to provide a very efficient illumination. Inother configurations, the phosphor is supported by one or more opticallytransparent member such that the light is free to emit in all directionsfrom the phosphor point source. In one variation, the phosphor is fullysurrounded in or encapsulated by an optically transparent material suchas a solid material like SiC, diamond, GaN, or other, or a liquidmaterial like water or a more thermally conductive liquid.

In another variation, the support member could also serve as a waveguidefor the laser light to reach the phosphor. In another variation, thesupport member could also serve as a protective safety measure to ensurethat no direct emitting laser light is exposed as it travels to reachthe phosphor. Such point sources of light that produce trueomni-directional emission are increasing useful as the point sourcebecomes increasing smaller, due to the fact that product of the emissionaperture and the emission angle is conserved or lost as subsequentoptics and reflectors are added. Specifically, for example, a smallpoint source can be collimated with small optics or reflectors. However,if the same small optics or reflector assembly are applied to a largepoint source, the optical control and collimation is diminished.

In all of the side pumped and transmissive embodiments of this inventionthe additional features and designs can be included. For example shapingof the excitation laser beam for optimizing the beam spotcharacteristics on the phosphor can be achieved by careful designconsiderations of the laser beam incident angle to the phosphor or withusing integrated optics such as free space optics like collimating lens.Safety features can be included such as passive features like physicaldesign considerations and beam dumps and/or active features such asphotodetectors or thermistors that can be used in a closed loop to turnthe laser off when a signal is indicated.

A point source omni-directional light source is configurable intoseveral types of illumination patterns including 4-pi steradianillumination to provide a wide illumination to a three dimensionalvolume such as a room, lecture hall, or stadium. Moreover, opticalelements can be included to manipulate the generated white light toproduce highly directional illumination. In some embodiments reflectorssuch as parabolic reflectors or lenses such as collimating lenses areused to collimate the white light or create a spot light that could beapplicable in an automobile headlight, flashlight, spotlight, or otherlights. In other embodiments, the point source illumination can bemodified with cylindrical optics and reflectors into linearomni-directional illumination, or linear directional illumination.Additionally, the point source illumination coupled into planarwaveguides for planar 2-pi steradian emission, planar 4-pi steradianemission to produce glare-free illumination patterns that emit from aplane.

In another specific preferred embodiment of the integrated white lightsource, the present invention is configured for a reflective modephosphor operation. In one example the excitation laser beam enters thephosphor through the same primary surface as the useful white light isemitted from. That is, operated in reflective mode the phosphor couldhave a first primary surface configured for both receiving the incidentexcitation laser beam and emitting useful white light. In thisconfiguration, the phosphor is positioned in front of the laser facetoutputting the laser beam, wherein both the laser and the phosphor areconfigured on a support member. The gallium and nitrogen containinglaser diode is configured with a cavity that has a length greater than100 um, greater than 500 um, greater than 1000 um, or greater than 1500um long and a width greater than 1 um, greater than 10 um, greater than20 um, greater than 30 um, or greater than 45 um. The cavity isconfigured with a front facets and back facet on the end wherein thefront facet comprises the output facet and emits the laser beam incidenton the phosphor. The output facet may contain an optical coating toreduce the reflectivity in the cavity. The back facet can be coated witha high reflectivity coating to reduce the amount of light exiting theback facet of the laser diode. In one example, the phosphor can becomprised of Ce doped YAG and emits yellow emission. The phosphor may bea ceramic phosphor and could be a single crystal phosphor. The phosphoris preferably shaped as a substantially flat member such as a plate or asheet with a shape such as a square, rectangle, polygon, circle, orellipse, and is characterized by a thickness. In a preferred embodimentthe length, width, and or diameter dimensions of the large surface areaof the phosphor are larger than the thickness of the phosphor. Forexample, the diameter, length, and/or width dimensions may be 2× greaterthan the thickness, 5× greater than the thickness, 10× greater than thethickness, or 50× greater than the thickness. Specifically, the phosphorplate may be configured as a circle with a diameter of greater than 50um, greater than 100 um, greater than 200 um, greater than 500 um,greater than 1 mm, or greater than 10 mm and a thickness of less than500 um, less than 200 um, less than 100 um or less than 50 um.

In one example of the reflective mode CPoS white light source embodimentof this invention optical coatings, material selections are made, orspecial design considerations are taken to improve the efficiency bymaximizing the amount of light exiting the primary surface of thephosphor. In one example, the backside of the phosphor may be coatedwith reflective layers or have reflective materials positioned on theback surface of the phosphor adjacent to the primary emission surface.The reflective layers, coatings, or materials help to reflect the lightthat hits the back surface of the phosphor such that the light willbounce and exit through the primary surface where the useful light iscaptured. In one example, a coating configured to increase thereflectivity for yellow light and blue light and is applied to thephosphor prior to attaching the phosphor to the common support member.In an another example, a reflective material is used as a bonding mediumthat attaches the phosphor to the support member or to an intermediatesubmount member. Examples of reflective materials include reflectivesolders and reflective glues, but could be others. With respect toattaching the phosphor to the common support member, thermal impedanceis a key consideration. The thermal impedance of this attachment jointshould be minimized using the best attaching material, interfacegeometry, and attachment process practices for the lowest thermalimpedance with sufficient reflectivity. Examples include AuSn solders,SAC solders, lead containing solders, indium solders, indium, and othersolders. The joint could also be formed from thermally conductive glues,thermal epoxies, and other materials. The common support member with thelaser and phosphor material is configured to provide thermal impedanceof less than 10 degrees Celsius per watt or less than 5 degrees Celsiusper watt of dissipated power characterizing a thermal path from thelaser device to a heat sink. The support member is comprised of athermally conductive material such as copper, copper tungsten, aluminum,SiC, sapphire, AlN, or other metals, ceramics, or semiconductors. Thereflective mode white light source apparatus has a form factorcharacterized by a length, a width, and a height. In an example, theheight is characterized by a dimension of less than 25 mm and greaterthan 0.5 mm, although there may be variations. In an alternativeexample, the height is characterized by a dimension of less than 12.5mm, and greater than 0.5 mm, although there may be variations. In yet analternative example, the length and width are characterized by adimension of less than 30 mm, less than 15 mm, or less than 5 mm,although there may be variations.

The reflective mode integrated white light source embodiment of thisinvention is configured with the phosphor member attached to the commonsupport member with the large primary surface configured for receivinglaser excitation light and emitting useful white light positioned at anangle normal (about 90 degrees) or off-normal (about 0 degrees to about89 degrees) to the axis of the laser diode output beam functioning toexcite the phosphor. That is, the laser output beam is pointing towardthe phosphor's emission surface at an angle of between 0 and 90 degrees.The nature of this configuration wherein the laser beam is not directedin the same direction the primary phosphor emission surface emits is abuilt in safety feature. That is, the laser beam is directed away fromor opposite of the direction the useful white light will exit thephosphor. As a result, if the phosphor is to break or get damaged duringnormal operation or from tampering, the laser beam would not be directedto the outside world where it could be harmful. Instead, the laser beamwould be incident on the backing surface where the phosphor wasattached. As a result, the laser beam could be scattered or absorbedinstead of exiting the white light source and into the surroundingenvironment. Additional safety measure can be taken such as using a beamdump feature or use of an absorbing material.

One example of this reflective mode integrated white light sourceembodiment is configured with the laser beam normal to the primaryphosphor emission surface. In this configuration the laser diode wouldbe positioned in front of the primary emission surface of the phosphorwhere it could impede the useful white light emitted from the phosphor.In a preferable embodiment of this reflective mode integrated whitelight source, the laser beam would be configured with an incident anglethat is off-axis to the phosphor such that it hits the phosphor surfaceat an angle of between 0 and 89 degrees or at a “grazing” angle. In thispreferable embodiment the laser diode device is positioned to the sideof the phosphor instead of in front of the phosphor where it will notsubstantially block or impede the emitted white light. Moreover, in thisconfiguration the built in safety feature is more optimal than in thenormal incidence configuration since when incident at an angle in thecase of phosphor damage or removal the incident laser beam would notreflect directly off the back surface of the support member where thephosphor was attached. By hitting the surface at an off-angle or agrazing angle any potential reflected components of the beam can bedirected to stay within the apparatus and not exit the outsideenvironment where it can be a hazard to human beings, animals, and theenvironment.

In all of the reflective mode embodiments of this invention theadditional features and designs can be included. For example shaping ofthe excitation laser beam for optimizing the beam spot characteristicson the phosphor can be achieved by careful design considerations of thelaser beam incident angle to the phosphor or with using integratedoptics such as free space optics like collimating lens. Safety featurescan be included such as passive features like physical designconsiderations and beam dumps and/or active features such asphotodetectors or thermistors that can be used in a closed loop or atype of feedback loop to turn the laser off when a signal is indicated.Moreover, optical elements can be included to manipulate the generatedwhite light. In some embodiments reflectors such as parabolic reflectorsor lenses such as collimating lenses are used to collimate the whitelight or create a spot light that could be applicable in an automobileheadlight, flashlight, spotlight, or other lights.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the latter portions of thespecification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified diagram illustrating a laser diode deviceconfigured on a semipolar substrate according to the present invention.

FIG. 2 is a simplified diagram illustrating a laser diode deviceconfigured on a polar c-plane substrate according to the presentinvention.

FIG. 3 is a simplified schematic cross-section of conventional ridgelaser diode-plane substrate according to the present invention.

FIG. 4 is a simplified diagram illustrating a conventional laser diodechip on submount (CoS) according to the present invention.

FIG. 5 is a simplified diagram illustrating epitaxy preparation processflow for epi transfer to a carrier wafer according to the presentinvention.

FIG. 6 is a simplified diagram illustrating a bond then etch processflow for epi layer transfer to a carrier wafer according to the presentinvention.

FIG. 7 is a simplified diagram illustrating a side view of die expansionwith selective area bonding according to the present invention.

FIG. 8 is a simplified diagram illustrating an example of an LDepitaxial structure according to the epitaxial transfer embodimentaccording to the present invention.

FIG. 9 is a simplified diagram illustrating an example of an LD devicestructure formed on carrier wafer from epitaxial structure in FIG. 8according to the present invention.

FIG. 10 is a simplified diagram illustrating a chip on submount (CoS)fabricated via wafer-level laser processing after transfer of galliumand nitrogen containing epitaxial layers according to an embodiment ofthe present invention.

FIG. 11 is a simplified diagram illustrating an integrated laser-basedwhite light source with a laser diode and phosphor member integratedonto a submount wherein the phosphor is configured for transmissiveoperation according to an embodiment of the present invention.

FIG. 12 is a simplified diagram illustrating an integrated laser-basedwhite light source with a laser diode fabricated in gallium and nitrogencontaining epitaxial layers transferred to a submount member and aphosphor member integrated onto the submount member wherein the phosphoris configured for transmissive operation according to an embodiment ofthe present invention.

FIG. 13 is a simplified diagram illustrating the apparatus configurationof FIG. 12 but with modification of the phosphor configured with acoating or modification to increase the useful white light outputaccording to an embodiment of the present invention.

FIG. 14 is a simplified diagram illustrating an example of an ellipticalprojected laser beam from a conventional laser diode according to anembodiment of the present invention.

FIG. 15 is a simplified diagram illustrating a side view diagram of alaser beam at normal incidence to a phosphor member according to anembodiment of the present invention.

FIG. 16 is a plot illustrating an example calculation of the ellipticalbeam diameters and ratio of beam diameters versus emitter distance fromphosphor according to an embodiment of the present invention.

FIG. 17 is a simplified diagram illustrating the apparatus configurationof FIG. 12 but with modification of the laser beam configured through acollimating optic prior to incidence on the phosphor according to anembodiment of the present invention.

FIG. 18 is a simplified diagram illustrating an example of anexacerbated elliptical laser beam profile from a conventional laserdiode with a projection surface tilted with respect to the fast axis ofthe laser diode the according to an embodiment of the present invention.

FIG. 19 is a simplified diagram illustrating an example of a morecircularized laser beam profile from a conventional laser diode with aprojection surface tilted with respect to the slow axis of the laserdiode the according to an embodiment of the present invention.

FIG. 20 is a simplified diagram illustrating a side view diagram of alaser beam projected on a phosphor member at a tilted orientationaccording to an embodiment of the present invention.

FIG. 21 is a plot illustrating an example calculation of the ellipticalbeam diameters and ratio of beam diameters versus emitter distance fromphosphor tilted at an angle of 33 degrees with respect to the slow axisaccording to an embodiment of the present invention.

FIG. 22 is a simplified diagram illustrating an integrated laser-basedwhite light source with a laser diode and phosphor member integratedonto a submount wherein the phosphor is configured at an angle with therespect to the laser diode for a beam shaping according to an embodimentof the present invention.

FIG. 23 is a simplified diagram illustrating an integrated laser-basedwhite light source with a laser diode fabricated in gallium and nitrogencontaining epitaxial layers transferred to a submount member and aphosphor member integrated onto the submount member wherein the phosphoris configured at an angle with the respect to the laser diode for a beamshaping according to an embodiment of the present invention.

FIG. 24 is a simplified diagram illustrating an integrated laser-basedwhite light source with a laser diode fabricated in gallium and nitrogencontaining epitaxial layers transferred to a submount member and aphosphor member integrated onto the submount member wherein the phosphoris configured as point source according to an embodiment of the presentinvention.

FIG. 25 is a simplified diagram illustrating an integrated laser-basedwhite light source with a laser diode and phosphor member integratedonto a common support member wherein the phosphor is configured forreflective operation and the laser beam has an off-normal incidence tothe phosphor according to an embodiment of the present invention.

FIG. 26 is a simplified diagram illustrating an integrated laser-basedwhite light source with a laser diode and phosphor member integratedonto a common support member wherein the phosphor is configured foroff-axis reflective operation and the laser beam is configured with acollimating or shaping optic according to an embodiment of the presentinvention.

FIG. 27 is a plot illustrating an example calculation of the ellipticalbeam diameters and ratio of beam diameters versus emitter distance fromphosphor tilted at an angle of 45 degrees with respect to the fast axisand 22 degrees with respect to the slow axis for a reflective phosphoroperation according to an embodiment of the present invention.

FIG. 28 is a simplified diagram illustrating an integrated laser-basedwhite light source with a laser diode and phosphor member integratedonto a common support member wherein the phosphor is configured forreflective operation and the laser beam has a dual axis rotation withrespect to the phosphor for an off-normal incidence to the phosphor withrespect to both the slow and fast axis according to an embodiment of thepresent invention.

FIG. 29 is a simplified diagram illustrating a transmissive modephosphor integrated laser-based white light source mounted in a can-typepackage according to an embodiment of the present invention.

FIG. 30 is a simplified diagram illustrating a transmissive modephosphor integrated laser-based white light source mounted in a can-typepackage and sealed with a cap member according to an embodiment of thepresent invention.

FIG. 31 is a simplified diagram illustrating a reflective mode phosphorintegrated laser-based white light source mounted in a surface mountpackage according to an embodiment of the present invention.

FIG. 32 is a simplified diagram illustrating a reflective mode phosphorintegrated laser-based white light source mounted in a surfacemount-type package and sealed with a cap member according to anembodiment of the present invention.

FIG. 33 is a simplified diagram illustrating a reflective mode phosphorintegrated laser-based white light source mounted in a surface mountpackage with an integrated beam dump safety feature according to anembodiment of the present invention.

FIG. 34 is a simplified diagram illustrating a reflective mode phosphorintegrated laser-based white light source mounted in a surfacemount-type package, sealed with a cap member, and mounted on a heat-sinkaccording to an embodiment of the present invention.

FIG. 35 is a simplified diagram illustrating a reflective mode phosphorintegrated laser-based white light source mounted in a flat-type packagewith a collimating optic according to an embodiment of the presentinvention.

FIG. 36 is a simplified diagram illustrating a transmissive modephosphor integrated laser-based white light source mounted in aflat-type package with a collimating optic according to an embodiment ofthe present invention.

FIG. 37 is a simplified diagram illustrating an integrated laser-basedwhite light source mounted in a flat-type package and sealed with a capmember according to an embodiment of the present invention.

FIG. 38 is a simplified diagram illustrating an integrated laser-basedwhite light source operating in transmissive mode with a collimatinglens according to an embodiment of the present invention.

FIG. 39 is a simplified diagram illustrating an integrated laser-basedwhite light source operating in reflective mode with a collimatingreflector according to an embodiment of the present invention.

FIG. 40 is a simplified diagram illustrating an integrated laser-basedwhite light source operating in reflective mode with a collimating lensaccording to an embodiment of the present invention.

FIG. 41 is a simplified diagram illustrating an integrated laser-basedwhite light source mounted in a can-type package with a collimatingreflector according to an embodiment of the present invention.

FIG. 42 is a simplified diagram illustrating an integrated laser-basedwhite light source mounted in a can-type package with a collimating lensaccording to an embodiment of the present invention.

FIG. 43 is a simplified diagram illustrating a reflective mode phosphorintegrated laser-based white light source mounted in a surface mounttype package mounted on a heat sink with a collimating reflectoraccording to an embodiment of the present invention.

FIG. 44 is a simplified diagram illustrating a reflective mode phosphorintegrated laser-based white light source mounted in a surface mounttype package mounted on a heat sink with a collimating lens according toan embodiment of the present invention.

FIG. 45 is a simplified diagram illustrating a reflective mode phosphorintegrated laser-based white light source mounted in a surface mounttype package mounted on a heat sink with a collimating lens andreflector member according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method and device for emitting whitecolored electromagnetic radiation using a combination of laser diodeexcitation sources based on gallium and nitrogen containing materialsand light emitting source based on phosphor materials. In this inventiona violet, blue, or other wavelength laser diode source based on galliumand nitrogen materials is closely integrated with phosphor materials toform a compact, high-brightness, and highly-efficient, white lightsource.

As background, while LED-based light sources offer great advantages overincandescent based sources, there are still challenges and limitationsassociated with LED device physics. The first limitation is the socalled “droop” phenomenon that plagues GaN based LEDs. The droop effectleads to power rollover with increased current density, which forcesLEDs to hit peak external quantum efficiency at very low currentdensities in the 10-200 A/cm2 range. Thus, to maximize efficiency of theLED based light source, the current density must be limited to lowvalues where the light output is also limited. The result is low outputpower per unit area of LED die [flux], which forces the use large LEDdie areas to meet the brightness requirements for most applications. Forexample, a typical LED based light bulb will require 3 mm2 to 30 mm2 ofepi area. A second limitation of LEDs is also related to theirbrightness, more specifically it is related to their spatial brightness.A conventional high brightness LED emits ˜1 W per mm² of epi area. Withsome advances and breakthrough perhaps this can be increased up to 5-10×to 5-10 W per mm² of epi area. Finally, LEDs fabricated on conventionalc-plane GaN suffer from strong internal polarization fields, whichspatially separate the electron and hole wave functions and lead to poorradiative recombination efficiency. Since this phenomenon becomes morepronounced in InGaN layers with increased indium content for increasedwavelength emission, extending the performance of UV or blue GaN-basedLEDs to the blue-green or green regime has been difficult.

An exciting new class of solid-state lighting based on laser diodes israpidly emerging. Like an LED, a laser diode is a two-lead semiconductorlight source that that emits electromagnetic radiation. However, unlikethe output from an LED that is primarily spontaneous emission, theoutput of a laser diode is comprised primarily of stimulated emission.The laser diode contains a gain medium that functions to provideemission through the recombination of electron-hole pairs and a cavityregion that functions as a resonator for the emission from the gainmedium. When a suitable voltage is applied to the leads to sufficientlypump the gain medium, the cavity losses are overcome by the gain and thelaser diode reaches the so-called threshold condition, wherein a steepincrease in the light output versus current input characteristic isobserved. At the threshold condition, the carrier density clamps andstimulated emission dominates the emission. Since the droop phenomenonthat plagues LEDs is dependent on carrier density, the clamped carrierdensity within laser diodes provides a solution to the droop challenge.Further, laser diodes emit highly directional and coherent light withorders of magnitude higher spatial brightness than LEDs. For example, acommercially available edge emitting GaN-based laser diode can reliablyproduce about 2 W of power in an aperture that is 15 um wide by about0.5 um tall, which equates to over 250,000 W/mm2. This spatialbrightness is over 5 orders of magnitude higher than LEDs or put anotherway, 10,000 times brighter than an LED.

In 1960, the laser was demonstrated by Theodore H. Maiman at HughesResearch Laboratories in Malibu. This laser utilized a solid-state flashlamp-pumped synthetic ruby crystal to produce red laser light at 694 nm.Early visible laser technology comprised lamp pumped infrared solidstate lasers with the output wavelength converted to the visible usingspecialty crystals with nonlinear optical properties. For example, agreen lamp pumped solid state laser had 3 stages: electricity powerslamp, lamp excites gain crystal which lases at 1064 nm, 1064 nm goesinto frequency conversion crystal which converts to visible 532 nm. Theresulting green and blue lasers were called “lamped pumped solid statelasers with second harmonic generation” (LPSS with SHG) had wall plugefficiency of ˜1%, and were more efficient than Ar-ion gas lasers, butwere still too inefficient, large, expensive, fragile for broaddeployment outside of specialty scientific and medical applications. Toimprove the efficiency of these visible lasers, high power diode (orsemiconductor) lasers were utilized. These “diode pumped solid statelasers with SHG” (DPSS with SHG) had 3 stages: electricity powers 808 nmdiode laser, 808 nm excites gain crystal, which lases at 1064 nm, 1064nm goes into frequency conversion crystal which converts to visible 532nm. As high power laser diodes evolved and new specialty SHG crystalswere developed, it became possible to directly convert the output of theinfrared diode laser to produce blue and green laser light output. These“directly doubled diode lasers” or SHG diode lasers had 2 stages:electricity powers 1064 nm semiconductor laser, 1064 nm goes intofrequency conversion crystal which converts to visible 532 nm greenlight. These lasers designs are meant to improve the efficiency, costand size compared to DPSS-SHG lasers, but the specialty diodes andcrystals required make this challenging today.

Based on essentially all the pioneering work on GaN LEDs describedabove, visible laser diodes based on GaN technology have rapidly emergedover the past 20 years. Currently the only viable direct blue and greenlaser diode structures are fabricated from the wurtzite AlGaInN materialsystem. The manufacturing of light emitting diodes from GaN relatedmaterials is dominated by the heteroepitaxial growth of GaN on foreignsubstrates such as Si, SiC and sapphire. Laser diode devices operate atsuch high current densities that the crystalline defects associated withheteroepitaxial growth are not acceptable. Because of this, very lowdefect-density, free-standing GaN substrates have become the substrateof choice for GaN laser diode manufacturing. Unfortunately, such bulkGaN substrates are costly and not widely available in large diameters.For example, 2″ diameter is the most common laser-quality bulk GaNc-plane substrate size today with recent progress enabling 4″ diameter,which are still relatively small compared to the 6″ and greaterdiameters that are commercially available for mature substratetechnologies. Further details of the present invention can be foundthroughout the present specification and more particularly below.

Additional benefits are achieved over pre-existing techniques using thepresent invention. In particular, the present invention enables acost-effective white light source. In a specific embodiment, the presentoptical device can be manufactured in a relatively simple and costeffective manner. Depending upon the embodiment, the present apparatusand method can be manufactured using conventional materials and/ormethods according to one of ordinary skill in the art. In someembodiments of this invention the gallium and nitrogen containing laserdiode source is based on c-plane gallium nitride material and in otherembodiments the laser diode is based on nonpolar or semipolar galliumand nitride material. In one embodiment the white source is configuredfrom a chip on submount (CoS) with an integrated phosphor on thesubmount to form a chip and phosphor on submount (CPoS) white lightsource.

In various embodiments, the laser device and phosphor device are mountedon a common support member with or without intermediate submounts andthe phosphor materials are operated in a transmissive mode or areflective mode to result in a white emitting laser-based light source.Merely by way of example, the invention can be applied to applicationssuch as white lighting, white spot lighting, flash lights, automobileheadlights, all-terrain vehicle lighting, light sources used inrecreational sports such as biking, surfing, running, racing, boating,light sources used for drones, planes, robots, other mobile or roboticapplications, safety, counter measures in defense applications,multi-colored lighting, lighting for flat panels, medical, metrology,beam projectors and other displays, high intensity lamps, spectroscopy,entertainment, theater, music, and concerts, analysis fraud detectionand/or authenticating, tools, water treatment, laser dazzlers,targeting, communications, transformations, transportations, leveling,curing and other chemical treatments, heating, cutting and/or ablating,pumping other optical devices, other optoelectronic devices and relatedapplications, and source lighting and the like.

Laser diodes are ideal as phosphor excitation sources. With a spatialbrightness (optical intensity per unit area) greater than 10,000 timeshigher than conventional LEDs and the extreme directionality of thelaser emission, laser diodes enable characteristics unachievable by LEDsand other light sources. Specifically, since the laser diodes outputbeams carrying over 1 W, over 5 W, over 10 W, or even over 100 W can befocused to very small spot sizes of less than 1 mm in diameter, lessthan 500 microns in diameter, less than 100 microns in diameter, or evenless than 50 microns in diameter, power densities of over 1 W/mm2, 100W/mm2, or even over 2,500 W/mm2 can be achieved. When this very smalland powerful beam of laser excitation light is incident on a phosphormaterial a the ultimate point source of white light can be achieved.Assuming a phosphor conversion ratio of 200 lumens of emitted whitelight per optical watt of excitation light, a 5 W excitation power couldgenerate 1000 lumens in a beam diameter of 100 microns, or 50 microns,or less. Such a point source is game changing in applications such asspotlighting or range finding where parabolic reflectors or lensingoptics can be combined with the point source to create highly collimatedwhite light spots that can travel drastically higher distances than everpossible before using LEDs or bulb technology.

In one embodiment, the present invention provides a CPoS laser-basedwhite light source comprising a form factor characterized by a length, awidth, and a height. In an example, the height is characterized by adimension of less than 25 mm, and greater than 0.5 mm, although theremay be variations. In an alternative example, the height ischaracterized by a dimension of less than 12.5 mm, and greater than 0.5mm, although there may be variations. In yet an alternative example, thelength and width are characterized by a dimension of less than 30 mm,less than 15 mm, or less than 5 mm, although there may be variations.The apparatus has a support member and at least one gallium and nitrogencontaining laser diode devices and phosphor material overlying thesupport member. The laser device is capable of an emission of a laserbeam with a wavelength preferably in the blue region of 425 nm to 475 nmor in the ultra violet or violet region of 380 nm to 425 nm, but can beother such as in the cyan region of 475 nm to 510 nm or the green regionof 510 nm to 560 nm.

As used herein, the term GaN substrate is associated with GroupIII-nitride based materials including GaN, InGaN, AlGaN, or other GroupIII containing alloys or compositions that are used as startingmaterials. Such starting materials include polar GaN substrates (i.e.,substrate where the largest area surface is nominally an (h k l) planewherein h=k=0, and l is non-zero), non-polar GaN substrates (i.e.,substrate material where the largest area surface is oriented at anangle ranging from about 80-100 degrees from the polar orientationdescribed above towards an (h k l) plane wherein l=0, and at least oneof h and k is non-zero) or semi-polar GaN substrates (i.e., substratematerial where the largest area surface is oriented at an angle rangingfrom about +0.1 to 80 degrees or 110-179.9 degrees from the polarorientation described above towards an (h k l) plane wherein l=0, and atleast one of h and k is non-zero). Of course, there can be othervariations, modifications, and alternatives.

The laser diode device can be fabricated on a conventional orientationof a gallium and nitrogen containing film or substrate (e.g., GaN) suchas the polar c-plane, on a nonpolar orientation such as the m-plane, oron a semipolar orientation such as the {30-31}, {20-21}, {30-32},{11-22}, {10-11}, {30-3-1}, {20-2-1}, {30-3-2}, or offcuts of any ofthese polar, nonpolar, and semipolar planes within +/−10 degrees towardsa c-plane, and/or +/−10 degrees towards an a-plane, and/or +/−10 degreestowards an m-plane.

FIG. 1a is a simplified schematic diagram of an example of a polarc-plane laser diode formed on a gallium and nitrogen containingsubstrate with the cavity aligned in the m-direction with cleaved oretched mirrors. The laser stripe region is characterized by a cavityorientation substantially in an m-direction, which is substantiallynormal to an a-direction, but can be others such as cavity alignmentsubstantially in the a-direction. The laser strip region has a first end107 and a second end 109 and is formed on an m-direction on a {0001}gallium and nitrogen containing substrate having a pair of cleaved oretched mirror structures, which face each other. For example, thegallium nitride substrate member is a bulk GaN substrate characterizedby having a nonpolar or semipolar crystalline surface region, but can beothers. The bulk GaN substrate may have a surface dislocation densitybelow 10⁵ cm⁻² or 10⁵ to 10⁷ cm⁻². The nitride crystal or wafer maycomprise Al_(x)In_(y)Ga_(1-x-y)N, where 0≤x, y, x+y≤1. In one specificembodiment, the nitride crystal comprises GaN. In one or moreembodiments, the GaN substrate has threading dislocations, at aconcentration between about 10⁵ cm⁻² and about 10⁸ cm⁻², in a directionthat is substantially orthogonal or oblique with respect to the surface.

FIG. 1b is a simplified schematic diagram of an example of a semipolarplane laser diode formed on a gallium and nitrogen containing substratewith the cavity aligned in a projection of a c-direction with cleaved oretched mirrors. The laser stripe region is characterized by a cavityorientation substantially in a projection of a c-direction, which issubstantially normal to an a-direction, but can be others such as cavityalignment substantially in the a-direction. The laser strip region has afirst end 107 and a second end 109 and is formed on an semipolarsubstrate such as a {40-41}, {30-31}, {20-21}, {40-4-1}, {30-3-1},{20-2-1}, {20-21}, or an offcut of these planes within +/−5 degrees fromthe c-plane and a-plane gallium and nitrogen containing substrate. Forexample, the gallium and nitrogen containing substrate member is a bulkGaN substrate characterized by having a nonpolar or semipolarcrystalline surface region, but can be others. The bulk GaN substratemay have a surface dislocation density below 10⁵ cm⁻² or 10⁵ to 10⁷cm⁻². The nitride crystal or wafer may comprise Al_(x)In_(y)Ga_(1-x-y)N,where 0≤x, y, x+y≤1. In one specific embodiment, the nitride crystalcomprises GaN. In one or more embodiments, the GaN substrate hasthreading dislocations, at a concentration between about 10⁵ cm⁻² andabout 10⁸ cm⁻², in a direction that is substantially orthogonal oroblique with respect to the surface.

The example laser diode devices in FIGS. 1a and 1b have a pair ofcleaved or etched mirror structures, which face each other. The firstcleaved or etched facet comprises a reflective coating and the secondcleaved or etched facet comprises no coating, an antireflective coating,or exposes gallium and nitrogen containing material. The first cleavedor etched facet is substantially parallel with the second cleaved oretched facet. The first and second cleaved facets are provided by ascribing and breaking process according to an embodiment oralternatively by etching techniques using etching technologies such asreactive ion etching (RIE), inductively coupled plasma etching (ICP), orchemical assisted ion beam etching (CAIBE), or other method. The firstand second mirror surfaces each comprise a reflective coating. Thecoating is selected from silicon dioxide, hafnia, and titania, tantalumpentoxide, zirconia, including combinations, and the like. Dependingupon the design, the mirror surfaces can also comprise ananti-reflective coating.

In a specific embodiment, the method of facet formation includessubjecting the substrates to a laser for pattern formation. In apreferred embodiment, the pattern is configured for the formation of apair of facets for one or more ridge lasers. In a preferred embodiment,the pair of facets face each other and are in parallel alignment witheach other. In a preferred embodiment, the method uses a UV (355 nm)laser to scribe the laser bars. In a specific embodiment, the laser isconfigured on a system, which allows for accurate scribe linesconfigured in one or more different patterns and profiles. In one ormore embodiments, the laser scribing can be performed on the back-side,front-side, or both depending upon the application. Of course, there canbe other variations, modifications, and alternatives.

In a specific embodiment, the method uses backside laser scribing or thelike. With backside laser scribing, the method preferably forms acontinuous line laser scribe that is perpendicular to the laser bars onthe backside of the GaN substrate. In a specific embodiment, the laserscribe is generally about 15-20 um deep or other suitable depth.Preferably, backside scribing can be advantageous. That is, the laserscribe process does not depend on the pitch of the laser bars or otherlike pattern. Accordingly, backside laser scribing can lead to a higherdensity of laser bars on each substrate according to a preferredembodiment. In a specific embodiment, backside laser scribing, however,may lead to residue from the tape on one or more of the facets. In aspecific embodiment, backside laser scribe often requires that thesubstrates face down on the tape. With front-side laser scribing, thebackside of the substrate is in contact with the tape. Of course, therecan be other variations, modifications, and alternatives.

It is well known that etch techniques such as chemical assisted ion beametching (CAIBE), inductively coupled plasma (ICP) etching, or reactiveion etching (RIE) can result in smooth and vertical etched sidewallregions, which could serve as facets in etched facet laser diodes. Inthe etched facet process a masking layer is deposited and patterned onthe surface of the wafer. The etch mask layer could be comprised ofdielectrics such as silicon dioxide (SiO2), silicon nitride (SixNy), acombination thereof or other dielectric materials. Further, the masklayer could be comprised of metal layers such as Ni or Cr, but could becomprised of metal combination stacks or stacks comprising metal anddielectrics. In another approach, photoresist masks can be used eitheralone or in combination with dielectrics and/or metals. The etch masklayer is patterned using conventional photolithography and etch steps.The alignment lithography could be performed with a contact aligner orstepper aligner. Such lithographically defined mirrors provide a highlevel of control to the design engineer. After patterning of thephotoresist mask on top of the etch mask is complete, the patterns inthen transferred to the etch mask using a wet etch or dry etchtechnique. Finally, the facet pattern is then etched into the waferusing a dry etching technique selected from CAIBE, ICP, RIE and/or othertechniques. The etched facet surfaces must be highly vertical of betweenabout 87 and about 93 degrees or between about 89 and about 91 degreesfrom the surface plane of the wafer. The etched facet surface regionmust be very smooth with root mean square roughness values of less thanabout 50 nm, 20 nm, 5 nm, or 1 nm. Lastly, the etched must besubstantially free from damage, which could act as nonradiativerecombination centers and hence reduce the catastrophic optical mirrordamage (COMD) threshold. CAIBE is known to provide very smooth and lowdamage sidewalls due to the chemical nature of the etch, while it canprovide highly vertical etches due to the ability to tilt the waferstage to compensate for any inherent angle in etch.

The laser stripe is characterized by a length and width. The lengthranges from about 50 microns to about 3000 microns, but is preferablybetween about 10 microns and about 400 microns, between about 400microns and about 800 microns, or about 800 microns and about 1600microns, but could be others. The stripe also has a width ranging fromabout 0.5 microns to about 50 microns, but is preferably between about0.8 microns and about 2.5 microns for single lateral mode operation orbetween about 2.5 um and about 50 um for multi-lateral mode operation,but can be other dimensions. In a specific embodiment, the presentdevice has a width ranging from about 0.5 microns to about 1.5 microns,a width ranging from about 1.5 microns to about 3.0 microns, a widthranging from about 3.0 microns to about 50 microns, and others. In aspecific embodiment, the width is substantially constant in dimension,although there may be slight variations. The width and length are oftenformed using a masking and etching process, which are commonly used inthe art.

The laser stripe is provided by an etching process selected from dryetching or wet etching. The device also has an overlying dielectricregion, which exposes a p-type contact region. Overlying the contactregion is a contact material, which may be metal or a conductive oxideor a combination thereof. The p-type electrical contact may be depositedby thermal evaporation, electron beam evaporation, electroplating,sputtering, or another suitable technique. Overlying the polished regionof the substrate is a second contact material, which may be metal or aconductive oxide or a combination thereof and which comprises the n-typeelectrical contact. The n-type electrical contact may be deposited bythermal evaporation, electron beam evaporation, electroplating,sputtering, or another suitable technique.

Given the high gallium and nitrogen containing substrate costs,difficulty in scaling up gallium and nitrogen containing substrate size,the inefficiencies inherent in the processing of small wafers, andpotential supply limitations it becomes extremely desirable to maximizeutilization of available gallium and nitrogen containing substrate andoverlying epitaxial material. In the fabrication of lateral cavity laserdiodes, it is typically the case that minimum die size is determined bydevice components such as the wire bonding pads or mechanical handlingconsiderations, rather than by laser cavity widths. Minimizing die sizeis critical to reducing manufacturing costs as smaller die sizes allow agreater number of devices to be fabricated on a single wafer in a singleprocessing run. The current invention is a method of maximizing thenumber of devices which can be fabricated from a given gallium andnitrogen containing substrate and overlying epitaxial material byspreading out the epitaxial material onto a carrier wafer via a dieexpansion process.

In certain embodiments, GaN surface orientation is substantially in thec-plane, m-plane, {40-41}, {30-31}, {20-21}, {40-4-1}, {30-3-1},{20-2-1} {20-21} orientation, and the device has a laser stripe regionformed overlying a portion of the off-cut crystalline orientationsurface region. For example, the laser stripe region is characterized bya cavity orientation substantially in a projection of a c-direction,which is substantially normal to an a-direction. In a specificembodiment, the laser strip region has a first end 107 and a second end109. In a preferred embodiment wherein the laser is formed on asemipolar orientation, the device is formed on a projection of ac-direction on a gallium and nitrogen containing substrate having a pairof cleaved mirror structures, which face each other.

In a preferred embodiment, the device has a first cleaved facet providedon the first end of the laser stripe region and a second cleaved facetprovided on the second end of the laser stripe region. In one or moreembodiments, the first cleaved is substantially parallel with the secondcleaved facet. Mirror surfaces are formed on each of the cleavedsurfaces. The first cleaved facet comprises a first mirror surface. In apreferred embodiment, the first mirror surface is provided by a top-sideskip-scribe scribing and breaking process. The scribing process can useany suitable techniques, such as a diamond scribe or laser scribe orcombinations. In a specific embodiment, the first mirror surfacecomprises a reflective coating. The reflective coating is selected fromsilicon dioxide, hafnia, and titania, tantalum pentoxide, zirconia,including combinations, and the like. The first mirror surface can alsohave an anti-reflective coating.

Also in a preferred embodiment, the second cleaved facet comprises asecond mirror surface. The second mirror surface is provided by a topside skip-scribe scribing and breaking process according to a specificembodiment. Preferably, the scribing is diamond scribed or laser scribedor the like. In a specific embodiment, the second mirror surfacecomprises a reflective coating, such as silicon dioxide, hathia, andtitania, tantalum pentoxide, zirconia, combinations, and the like. In aspecific embodiment, the second mirror surface has an anti-reflectivecoating.

In a specific embodiment on a nonpolar Ga-containing substrate, thedevice is characterized by a spontaneously emitted light is polarized insubstantially perpendicular to the c-direction. In a preferredembodiment, the spontaneously emitted light is characterized by apolarization ratio of greater than 0.1 to about 1 perpendicular to thec-direction. In a preferred embodiment, the spontaneously emitted lightcharacterized by a wavelength ranging from about 430 nanometers to about470 nm to yield a blue emission, or about 500 nanometers to about 540nanometers to yield a green emission, and others. For example, thespontaneously emitted light can be violet (e.g., 395 to 420 nanometers),blue (e.g., 420 to 470 nm); green (e.g., 500 to 540 nm), or others. In apreferred embodiment, the spontaneously emitted light is highlypolarized and is characterized by a polarization ratio of greater than0.4. In another specific embodiment on a semipolar {20-21} Ga-containingsubstrate, the device is also characterized by a spontaneously emittedlight is polarized in substantially parallel to the a-direction orperpendicular to the cavity direction, which is oriented in theprojection of the c-direction.

In a specific embodiment, the present invention provides an alternativedevice structure capable of emitting 501 nm and greater light in a ridgelaser embodiment. The device is provided with one or more of thefollowing epitaxially grown elements:

-   -   an n-GaN or n-AlGaN cladding layer with a thickness from 100 nm        to 3000 nm with Si doping level of 5E17 cm⁻³ to 3E18 cm⁻³;    -   an n-side SCH layer comprised of InGaN with molar fraction of        indium of between 2% and 10% and thickness from 20 nm to 250 nm;    -   multiple quantum well active region layers comprised of at least        two 2.0 nm to 8.5 nm InGaN quantum wells separated by 1.5 nm and        greater, and optionally up to about 12 nm, GaN or InGaN        barriers;    -   a p-side SCH layer comprised of InGaN with molar a fraction of        indium of between 1% and 10% and a thickness from 15 nm to 250        nm or an upper GaN-guide layer;    -   an electron blocking layer comprised of AlGaN with molar        fraction of aluminum of between 0% and 22% and thickness from 5        nm to 20 nm and doped with Mg;    -   a p-GaN or p-AlGaN cladding layer with a thickness from 400 nm        to 1500 nm with Mg doping level of 2E17 cm⁻³ to 2E19 cm-3; and    -   a p++-GaN contact layer with a thickness from 20 nm to 40 nm        with Mg doping level of 1E19 cm⁻³ to 1E21 cm⁻³.

FIG. 3 is a cross-sectional view of a laser device 200. As shown, thelaser device includes gallium nitride substrate 203, which has anunderlying n-type metal back contact region 201. For example, thesubstrate 203 may be characterized by a semipolar or nonpolarorientation. The device also has an overlying n-type gallium nitridelayer 205, an active region 207, and an overlying p-type gallium nitridelayer structured as a laser stripe region 209. Each of these regions isformed using at least an epitaxial deposition technique of metal organicchemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), orother epitaxial growth techniques suitable for GaN growth. The epitaxiallayer is a high quality epitaxial layer overlying the n-type galliumnitride layer. In some embodiments the high quality layer is doped, forexample, with Si or O to form n-type material, with a dopantconcentration between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

An n-type Al_(u)In_(v)Ga_(1-u-v)N layer, where 0≤u, v, u+v≤1, isdeposited on the substrate. The carrier concentration may lie in therange between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³. The deposition may beperformed using metalorganic chemical vapor deposition (MOCVD) ormolecular beam epitaxy (MBE).

For example, the bulk GaN substrate is placed on a susceptor in an MOCVDreactor. After closing, evacuating, and back-filling the reactor (orusing a load lock configuration) to atmospheric pressure, the susceptoris heated to a temperature between about 1000 and about 1200 degreesCelsius in the presence of a nitrogen-containing gas. The susceptor isheated to approximately 900 to 1200 degrees Celsius under flowingammonia. A flow of a gallium-containing metalorganic precursor, such astrimethylgallium (TMG) or triethylgallium (TEG) is initiated, in acarrier gas, at a total rate between approximately 1 and 50 standardcubic centimeters per minute (sccm). The carrier gas may comprisehydrogen, helium, nitrogen, or argon. The ratio of the flow rate of thegroup V precursor (ammonia) to that of the group III precursor(trimethylgallium, triethylgallium, trimethylindium, trimethylaluminum)during growth is between about 2000 and about 12000. A flow of disilanein a carrier gas, with a total flow rate of between about 0.1 sccm and10 sccm, is initiated.

In one embodiment, the laser stripe region is p-type gallium nitridelayer 209. The laser stripe is provided by a dry etching process, butwet etching can be used. The dry etching process is an inductivelycoupled process using chlorine bearing species or a reactive ion etchingprocess using similar chemistries. The chlorine bearing species arecommonly derived from chlorine gas or the like. The device also has anoverlying dielectric region, which exposes 213 contact region. Thedielectric region is an oxide such as silicon dioxide or siliconnitride, and a contact region is coupled to an overlying metal layer215. The overlying metal layer is preferably a multilayered structurecontaining gold and platinum (Pt/Au), palladium and gold (Pd/Au), ornickel gold (Ni/Au), or a combination thereof.

Active region 207 preferably includes one to ten quantum well regions ora double heterostructure region for light emission. Following depositionof the n-type Al_(u)In_(v)Ga_(1-u-v)N layer to achieve a desiredthickness, an active layer is deposited. The quantum wells arepreferably InGaN with GaN, AlGaN, InAlGaN, or InGaN barrier layersseparating them. In other embodiments, the well layers and barrierlayers comprise Al_(w)In_(x)Ga_(1-w-x)N and Al_(y)In_(z)Ga_(1-y-z)N,respectively, where 0≤w, x, y, z, w+x, y+z≤1, where w<u, y and/or x>v, zso that the bandgap of the well layer(s) is less than that of thebarrier layer(s) and the n-type layer. The well layers and barrierlayers each have a thickness between about 1 nm and about 20 nm. Thecomposition and structure of the active layer are chosen to providelight emission at a preselected wavelength. The active layer may be leftundoped (or unintentionally doped) or may be doped n-type or p-type.

The active region can also include an electron blocking region, and aseparate confinement heterostructure. The electron-blocking layer maycomprise Al_(s)In_(t)Ga_(1-s-t)N, where 0≤s, t, s+t≤1, with a higherbandgap than the active layer, and may be doped p-type. In one specificembodiment, the electron blocking layer includes AlGaN. In anotherembodiment, the electron blocking layer includes an AlGaN/GaNsuper-lattice structure, comprising alternating layers of AlGaN and GaN,each with a thickness between about 0.2 nm and about 5 nm.

As noted, the p-type gallium nitride or aluminum gallium nitridestructure is deposited above the electron blocking layer and activelayer(s). The p-type layer may be doped with Mg, to a level betweenabout 10¹⁶ cm⁻³ and 10²² cm⁻³, with a thickness between about 5 nm andabout 1000 nm. The outermost 1-50 nm of the p-type layer may be dopedmore heavily than the rest of the layer, so as to enable an improvedelectrical contact. The device also has an overlying dielectric region,for example, silicon dioxide, which exposes 213 contact region.

The metal contact is made of suitable material such as silver, gold,aluminum, nickel, platinum, rhodium, palladium, chromium, or the like.The contact may be deposited by thermal evaporation, electron beamevaporation, electroplating, sputtering, or another suitable technique.In a preferred embodiment, the electrical contact serves as a p-typeelectrode for the optical device. In another embodiment, the electricalcontact serves as an n-type electrode for the optical device. The laserdevices illustrated in FIGS. 1 and 2 and described above are typicallysuitable for relative low-power applications.

In various embodiments, the present invention realizes high output powerfrom a diode laser is by widening one or more portions of the lasercavity member from the single lateral mode regime of 1.0-3.0 μm to themulti-lateral mode range 5.0-20 μm. In some cases, laser diodes havingcavities at a width of 50 μm or greater are employed.

The laser stripe length, or cavity length ranges from 100 to 3000 μm andemploys growth and fabrication techniques such as those described inU.S. patent application Ser. No. 12/759,273, filed Apr. 13, 2010, whichis incorporated by reference herein. As an example, laser diodes arefabricated on nonpolar or semipolar gallium containing substrates, wherethe internal electric fields are substantially eliminated or mitigatedrelative to polar c-plane oriented devices. It is to be appreciated thatreduction in internal fields often enables more efficient radiativerecombination. Further, the heavy hole mass is expected to be lighter onnonpolar and semipolar substrates, such that better gain properties fromthe lasers can be achieved.

FIG. 3 illustrates an example cross-sectional diagram of a gallium andnitrogen based laser diode device. The epitaxial device structure isformed on top of the gallium and nitrogen containing substrate member203. The substrate member may be n-type doped with O and/or Si doping.The epitaxial structures will contain n-side layers 205 such as ann-type buffer layer comprised of GaN, AlGaN, AlINGaN, or InGaN andn-type cladding layers comprised of GaN, AlGaN, or AlInGaN. The n-typedlayers may have thickness in the range of 0.3 um to about 3 microns orto about 5 microns and may be doped with an n-type carriers such as Sior O to concentrations between 1E16 cm3 to 1E19 cm3. Overlying then-type layers is the active region and waveguide layers 207. This regioncould contain an n-side waveguide layer or separate confinementhetereostructure (SCH) such as InGaN to help with optical guiding of themode. The InGaN layer be comprised of 1 to 15% molar fraction of InNwith a thickness ranging from about 30 nm to about 250 nm and may bedoped with an n-type species such as Si. Overlying the SCH layer is thelight emitting regions which could be comprised of a doublehetereostructure or a quantum well active region. A quantum well activeregion could be comprised of 1 to 10 quantum wells ranging in thicknessfrom 1 nm to 20 nm comprised of InGaN. Barrier layers comprised of GaN,InGaN, or AlGaN separate the quantum well light emitting layers. Thebarriers range in thickness from 1 nm to about 25 nm. Overlying thelight emitting layers are optionally an AlGaN or InAlGaN electronblocking layer with 5% to about 35% AlN and optionally doped with ap-type species such as Mg. Also optional is a p-side waveguide layer orSCH such as InGaN to help with optical guiding of the mode. The InGaNlayer be comprised of 1 to 15% molar fraction of InN with a thicknessranging from 30 nm to about 250 nm and may be doped with an p-typespecies such as Mg. Overlying the active region and optional electronblocking layer and p-side waveguide layers is a p-cladding region and ap++ contact layer. The p-type cladding region is comprised of GaN,AlGaN, AlINGaN, or a combination thereof. The thickness of the p-typecladding layers is in the range of 0.3 um to about 2 microns and isdoped with Mg to a concentration of between 1E16 cm3 to 1E19 cm3. Aridge 211 is formed in the p-cladding region for lateral confinement inthe waveguide using an etching process selected from a dry etching or awet etching process. A dielectric material 213 such as silicon dioxideor silicon nitride or deposited on the surface region of the device andan opening is created on top of the ridge to expose a portion of the p++GaN layer. A p-contact 215 is deposited on the top of the device tocontact the exposed p++ contact region. The p-type contact may becomprised of a metal stack containing one or more of Au, Pd, Pt, Ni, Ti,or Ag and may be deposited with electron beam deposition, sputterdeposition, or thermal evaporation. A n-contact 201 is formed to thebottom of the substrate member. The n-type contact may be comprised of ametal stack containing one or more of Au, Al, Pd, Pt, Ni, Ti, or Ag andmay be deposited with electron beam deposition, sputter deposition, orthermal evaporation.

After the laser diode chip fabrication as described above, the laserdiode can be mounted to a submount. In some examples the submount iscomprised of AlN, SiC, BeO, diamond, or other materials such as metals,ceramics, or composites. The submount can be the common support memberwherein the phosphor member of the CPoS would also be attached.Alternatively, the submount can be an intermediate submount intended tobe mounted to the common support member wherein the phosphor material isattached. The submount member may be characterized by a width, length,and thickness. In an example wherein the submount is the common supportmember for the phosphor and the laser diode chip the submount would havea width and length ranging in dimension from about 0.5 mm to about 5 mmor to about 15 mm and a thickness ranging from about 150 um to about 2mm. In the example wherein the submount is an intermediate submountbetween the laser diode chip and the common support member it could becharacterized by width and length ranging in dimension from about 0.5 mmto about 5 mm and the thickness may range from about 50 um to about 500um. The laser diode is attached to the submount using a bonding process,a soldering process, a gluing process, or a combination thereof. In oneembodiment the submount is electrically isolating and has metal bondpads deposited on top. The laser chip is mounted to at least one ofthose metal pads. The laser chip can be mounted in a p-side down or ap-side up configuration. After bonding the laser chip, wire bonds areformed from the chip to the submount such that the final chip onsubmount (CoS) is completed and ready for integration.

A schematic diagram illustrating a CoS based on a conventional laserdiode formed on gallium and nitrogen containing substrate technologyaccording to this present invention is shown in FIG. 4. The CoS iscomprised of submount material 201 configured to act as an intermediatematerial between a laser diode chip 202 and a final mounting surface.The submount is configured with electrodes 203 and 205 that may beformed with deposited metal layers such as Au. In one example, Ti/Pt/Auis used for the electrodes. Wirebonds 204 are configured to couple theelectrical power from the electrodes 203 and 205 on the submount to thelaser diode chip to generate a laser beam output 206 from the laserdiode. The electrodes 203 and 205 are configured for an electricalconnection to an external power source such as a laser driver, a currentsource, or a voltage source. Wirebonds can be formed on the electrodesto couple electrical power to the laser diode device and activate thelaser.

In another embodiment, the gallium and nitrogen containing laser diodefabrication includes an epitaxial release step to lift off theepitaxially grown gallium and nitrogen layers and prepare them fortransfer to a carrier wafer which could comprise the submount afterlaser fabrication. The transfer step requires precise placement of theepitaxial layers on the carrier wafer to enable subsequent processing ofthe epitaxial layers into laser diode devices. The attachment process tothe carrier wafer could include a wafer bonding step with a bondinterface comprised of metal-metal, semicondonctor-semiconductor,glass-glass, dielectric-dielectric, or a combination thereof.

In yet another preferred variation of this CPoS white light source, aprocess for lifting-off gallium and nitrogen containing epitaxialmaterial and transferring it to the common support member can be used toattach the gallium and nitrogen containing laser epitaxial material to asubmount member. In this embodiment, the gallium and nitrogen epitaxialmaterial is released from the gallium and nitrogen containing substrateit was epitaxially grown on. As an example, the epitaxial material canbe released using a photoelectrochemical (PEC) etching technique. It isthen transferred to a submount material using techniques such as waferbonding wherein a bond interface is formed. For example, the bondinterface can be comprised of a Au—Au bond. The submount materialpreferably has a high thermal conductivity such as SiC, wherein theepitaxial material is subsequently processed to form a laser diode witha cavity member, front and back facets, and electrical contacts forinjecting current. After laser fabrication is complete, a phosphormaterial is introduced onto the submount to form an integrated whitelight source. The phosphor material may have an intermediate materialpositioned between the submount and the phosphor. The intermediatematerial may be comprised of a thermally conductive material such ascopper. The phosphor material can be attached to the submount usingconventional die attaching techniques using solders such as AuSn solder,but can be other techniques such as SAC solders, lead containingsolders, indium solders, or other attachment methods such as thermaladhesives. Optimizing the bond for the lowest thermal impedance is a keyparameter for heat dissipation from the phosphor, which is critical toprevent phosphor degradation and thermal quenching of the phosphormaterial. The benefits of using this embodiment with lifted-off andtransferred gallium and nitrogen containing material are the reducedcost, improved laser performance, and higher degree of flexibility forintegration using this technology.

In this embodiment, gallium and nitrogen containing epitaxial layers aregrown on a bulk gallium and nitrogen containing substrate. The epitaxiallayer stack comprises at least a sacrificial release layer and the laserdiode device layers overlying the release layers. Following the growthof the epitaxial layers on the bulk gallium and nitrogen containingsubstrate, the semiconductor device layers are separated from thesubstrate by a selective wet etching process such as a PEC etchconfigured to selectively remove the sacrificial layers and enablerelease of the device layers to one or more carrier wafers. In oneembodiment, a bonding material is deposited on the surface overlying thesemiconductor device layers. A bonding material is also deposited eitheras a blanket coating or patterned on a carrier wafer. Standardlithographic processes are used to selectively mask the semiconductordevice layers. The wafer is then subjected to an etch process such asdry etch or wet etch processes to define via structures that expose theone or more sacrificial layers on the sidewall of the mesa structure. Asused herein, the term mesa region or mesa is used to describe thepatterned epitaxial material on the gallium and nitrogen containingsubstrate and prepared for transfer to the carrier wafer. The mesaregion can be any shape or form including a rectangular shape, a squareshape, a triangular shape, a circular shape, an elliptical shape, apolyhedron shape, or other shape. The term mesa shall not limit thescope of the present invention.

Following the definition of the mesa, a selective etch process isperformed to fully or partially remove the one or more sacrificiallayers while leaving the semiconductor device layers intact. Theresulting structure comprises undercut mesas comprised of epitaxialdevice layers. The undercut mesas correspond to dice from whichsemiconductor devices will be formed on. In some embodiments aprotective passivation layer can be employed on the sidewall of the mesaregions to prevent the device layers from being exposed to the selectiveetch when the etch selectivity is not perfect. In other embodiments aprotective passivation is not needed because the device layers are notsensitive to the selective etch or measures are taken to prevent etchingof sensitive layers such as shorting the anode and cathode. The undercutmesas corresponding to device dice are then transferred to the carrierwafer using a bonding technique wherein the bonding material overlyingthe semiconductor device layers is joined with the bonding material onthe carrier wafer. The resulting structure is a carrier wafer comprisinggallium and nitrogen containing epitaxial device layers overlying thebonding region.

In a preferred embodiment PEC etching is deployed as the selective etchto remove the one or more sacrificial layers. PEC is a photo-assistedwet etch technique that can be used to etch GaN and its alloys. Theprocess involves an above-band-gap excitation source and anelectrochemical cell formed by the semiconductor and the electrolytesolution. In this case, the exposed (Al,In,Ga)N material surface acts asthe anode, while a metal pad deposited on the semiconductor acts as thecathode. The above-band-gap light source generates electron-hole pairsin the semiconductor. Electrons are extracted from the semiconductor viathe cathode while holes diffuse to the surface of material to form anoxide. Since the diffusion of holes to the surface requires the bandbending at the surface to favor a collection of holes, PEC etchingtypically works only for n-type material although some methods have beendeveloped for etching p-type material. The oxide is then dissolved bythe electrolyte resulting in wet etching of the semiconductor. Differenttypes of electrolyte including HCl, KOH, and HNO3 have been shown to beeffective in PEC etching of GaN and its alloys. The etch selectivity andetch rate can be optimized by selecting a favorable electrolyte. It isalso possible to generate an external bias between the semiconductor andthe cathode to assist with the PEC etching process.

The preparation of the epitaxy wafer is shown in FIG. 5. A substrate 100is overlaid by a buffer layer 101, a selectively removable sacrificiallayer 107, an buffer layer 101, a collection of device layers 102 and acontact layer 103. The sacrificial region is exposed by etching of viasthat extend below the sacrificial layer and segment the layers 101, 102,103, and 107 into mesas. A layer composed of bonding media 108 isdeposited overlaying the mesas. In some embodiments the bonding layer isdeposited before the sacrificial layer is exposed. Finally thesacrificial layer is removed via a selective process. This processrequires the inclusion of a buried sacrificial region, which can be PECetched selectively by bandgap. For GaN based semiconductor devices,InGaN layers such as quantum wells have been shown to be an effectivesacrificial region during PEC etching. The first step depicted in FIG. 5is a top down etch to expose the sacrificial layers, followed by abonding metal deposition as shown in FIG. 5. With the sacrificial regionexposed a bandgap selective PEC etch is used to undercut the mesas. Inone embodiment, the bandgaps of the sacrificial region and all otherlayers are chosen such that only the sacrificial region will absorblight, and therefor etch, during the PEC etch. Another embodiment of theinvention involving light emitting devices uses a sacrificial regionwith a higher bandgap than the active region such that both layers areabsorbing during the bandgap PEC etching process.

In one embodiment involving light emitting devices, the active regioncan be prevented from etching during the bandgap selective PEC etchusing an insulating protective layer on the sidewall. The device layersare exposed using an etch and an etch resistant protect layer isdeposited overlaying the edges of the device layers such that they arenot exposed to the etch chemicals. The sacrificial layer is then exposedby an etch of vias. A bonding layer is deposited and a selective etchprocess is used to remove the sacrificial layers. In some embodimentsthe bonding layer is deposited after the selective etch. This work flowis advantageous when the device layers are susceptible to damage fromthe etch process used to remove the sacrificial layer. With thesacrificial region exposed a bandgap selective PEC etch is used toundercut the mesas. At this point, the selective area bonding process isused to continue fabricating devices. In another embodiment the activeregion is exposed by the dry etch and the active region and sacrificialregions both absorb the pump light. A conductive path is fabricatedbetween the p-type and n-type cladding surrounding the active region. Asin a solar cell, carriers are swept from the active region due to theelectric field in the depletion region. By electrically connecting then-type and p-type layers together holes can be continually swept fromthe active region, slowing or preventing PEC etching. In otherembodiments involving electronic devices or power electronic devicesthat do not contain light emitting layers, no special measures need tobe taken to protect the semiconductor device layers during the selectiveetch.

Sacrificial layers for lift-off of the substrate via photochemicaletching would incorporate at a minimum a low-bandgap or doped layer thatwould absorb the pump light and have enhanced etch rate relative to thesurrounding material. The sacrificial layer can be deposited epitaxiallyand their alloy composition and doping of these can be selected suchthat hole carrier lifetime and diffusion lengths are high. Defects thatreduce hole carrier lifetimes and diffusion length must can be avoidedby growing the sacrificial layers under growth conditions that promotehigh material crystalline quality. An example of a sacrificial layerwould be InGaN layers that absorb at the wavelength of an external lightsource. An etch stop layer designed with very low etch rate to controlthe thickness of the adjacent material remaining after substrate removalcan also be incorporated to allow better control of the etch process.The etch properties of the etch stop layer can be controlled solely byor a combination of alloy composition and doping. A potential etch stoplayer would an AlGaN or GaN layer with a bandgap higher than theexternal light source. Another potential etch stop layer is a highlydoped n-type AlGaN or GaN layer with reduce minority carrier diffusionlengths and lifetime thereby dramatically reducing the etch rate of theetch stop material.

In some embodiments PEC etching is achieved without the use of an activeregion protecting layer by electrically shorting the p-side of the laserdiode pn-junction to the n-side. Etching in the PEC process is achievedby the dissolution of AlInGaN materials at the wafer surface when holesare transferred to the etching solution. These holes are then recombinedin the solution with electrons extracted at the cathode metal interfacewith the etching solution. Charge neutrality is therefore achieved.Selective etching is achieved by electrically shorting the anode to thecathode. Electron hole pairs generated in the device light emittinglayers are swept out of the light emitting layers by the electric fieldof the of the p-n junction. Since holes are swept out of the activeregion, there is little or no etching of the light emitting layer. Thebuildup of carriers produces a potential difference that drives carriersthrough the metal interconnects that short the anode and cathode wherethey recombine. The flat band conditions in the sacrificial regionresult in a buildup of holes that result in rapid etching of thesacrificial layers. In one embodiment, the metal interconnects to shortthe anode and cathode can be used as anchor regions to mechanically holdthe gallium and nitrogen containing mesas in place prior to the bondingstep.

The relative etch rates of the sacrificial and active regions aredetermined by a number of factors, but primarily it is determined by thedensity of holes found in the active region at steady state. If themetal interconnects or anchors are very resistive, or if either thecathode or anode electrical contacts to the p-type and n-type,respectively, cladding regions are too resistive or have large Schottkybarriers then it is possible for carriers to accumulate on either sideof the p-n junction. These carriers will produce an electric field thatacts against the field in the depletion region and will reduce themagnitude of the field in the depletion region until the rate ofphoto-generated carrier drift out of the active region is balanced bythe recombination rate of carriers via the metal layers shorting thecathode and anode. Some recombination will take place via photochemicaletching, and since this scales with the density of holes in the activeregion it is preferable to prevent the buildup of a photo-induced biasacross the active region.

In one embodiment thermocompression bonding is used to transfer thegallium and nitrogen epitaxial semiconductor layers to the carrierwafer. In this embodiment thermocompression bonding involves bonding ofthe epitaxial semiconductor layers to the carrier wafer at elevatedtemperatures and pressures using a bonding media disposed between theepitaxial layers and handle wafer. The bonding media may be comprised ofa number of different layers, but typically contain at least one layer(the bonding layer) that is composed of a relatively ductile materialwith a high surface diffusion rate. In many cases this material iscomprised of Au, Al or Cu. The bonding stack may also include layersdisposed between the bonding layer and the epitaxial materials or handlewafer that promote adhesion. For example an Au bonding layer on a Siwafer may result in diffusion of Si to the bonding interface, whichwould reduce the bonding strength. Inclusion of a diffusion barrier suchas silicon oxide or nitride would limit this effect. Relatively thinlayers of a second material may be applied on the top surface of thebonding layer in order to promote adhesion between the bonding layersdisposed on the epitaxial material and handle. Some bonding layermaterials of lower ductility than gold (e.g. Al, Cu etc.) or which aredeposited in a way that results in a rough film (for exampleelectrolytic deposition) may require planarization or reduction inroughness via chemical or mechanical polishing before bonding, andreactive metals may require special cleaning steps to remove oxides ororganic materials that may interfere with bonding.

Thermocompressive bonding can be achieved at relatively lowtemperatures, typically below 500 degrees Celsius and above 200.Temperatures should be high enough to promote diffusivity between thebonding layers at the bonding interface, but not so high as to promoteunintentional alloying of individual layers in each metal stack.Application of pressure enhances the bond rate, and leads to someelastic and plastic deformation of the metal stacks that brings theminto better and more uniform contact. Optimal bond temperature, time andpressure will depend on the particular bond material, the roughness ofthe surfaces forming the bonding interface and the susceptibility tofracture of the handle wafer or damage to the device layers under load.

The bonding interface need not be composed of the totality of the wafersurface. For example, rather than a blanket deposition of bonding metal,a lithographic process could be used to deposit metal in discontinuousareas separated by regions with no bonding metal. This may beadvantageous in instances where defined regions of weak or no bondingaid later processing steps, or where an air gap is needed. One exampleof this would be in removal of the GaN substrate using wet etching of anepitaxially grown sacrificial layer. To access the sacrificial layer onemust etch vias into either of the two surfaces of the epitaxial wafer,and preserving the wafer for re-use is most easily done if the vias areetched from the bonded side of the wafer. Once bonded, the etched viasresult in channels that can conduct etching solution from the edges tothe center of the bonded wafers, and therefore the areas of thesubstrate comprising the vias are not in intimate contact with thehandle wafer such that a bond would form.

The bonding media can also be an amorphous or glassy material bondedeither in a reflow process or anodically. In anodic bonding the media isa glass with high ion content where mass transport of material isfacilitated by the application of a large electric field. In reflowbonding the glass has a low melting point, and will form contact and agood bond under moderate pressures and temperatures. All glass bonds arerelatively brittle, and require the coefficient of thermal expansion ofthe glass to be sufficiently close to the bonding partner wafers (i.e.the GaN wafer and the handle). Glasses in both cases could be depositedvia vapor deposition or with a process involving spin on glass. In bothcases the bonding areas could be limited in extent and with geometrydefined by lithography or silk-screening process.

Gold-gold metallic bonding is used as an example in this work, althougha wide variety of oxide bonds, polymer bonds, wax bonds, etc., arepotentially suitable. Submicron alignment tolerances are possible usingcommercial available die bonding equipment. In another embodiment of theinvention the bonding layers can be a variety of bonding pairs includingmetal-metal, oxide-oxide, soldering alloys, photoresists, polymers, wax,etc. Only epitaxial die which are in contact with a bond bad on thecarrier wafer will bond. Sub-micron alignment tolerances are possible oncommercially available die or flip chip bonders.

In an example, an oxide is overlaid on an exposed planar n-type orp-type gallium and nitrogen containing material or over an exposedplanar n-type or p-type gallium and nitrogen containing material usingdirect wafer bonding of the surface of the gallium and nitrogencontaining material to the surface of a carrier wafer comprisedprimarily of an oxide or a carrier wafer with oxide layers disposed onthem. In both cases the oxide surface on the carrier wafer and theexposed gallium and nitrogen containing material are cleaned to reducethe amount of hydrocarbons, metal ions and other contaminants on thebonding surfaces. The bonding surfaces are then brought into contact andbonded at elevated temperature under applied pressure. In some cases thesurfaces are treated chemically with one or more of acids, bases orplasma treatments to produce a surface that yields a weak bond whenbrought into contact with the oxide surface. For example the exposedsurface of the gallium containing material may be treated to form a thinlayer of gallium oxide, which being chemically similar to the oxidebonding surface will bond more readily. Furthermore the oxide and nowgallium oxide terminated surface of the gallium and nitrogen containingmaterial may be treated chemically to encourage the formation ofdangling hydroxyl groups (among other chemical species) that will formtemporary or weak chemical or van der Waals bonds when the surfaces arebrought into contact, which are subsequently made permanent when treatedat elevated temperatures and elevated pressures.

In an alternative example, an oxide is deposited overlying the devicelayer mesa region to form a bond region. The carrier wafer is alsoprepared with an oxide layer to form a bond region. The oxide layeroverlying the carrier could be patterned or could be a blanket layer.The oxide surface on the carrier wafer and the oxide surface overlyingthe mesa device layer mesa regions are cleaned to reduce the amount ofhydrocarbons, metal ions and other contaminants on the bonding surfaces.The bonding surfaces are then brought into contact and bonded atelevated temperature under applied pressure. In one embodiment, achemical mechanical polish (CMP) process is used to planarize the oxidesurface and make them smooth to improve the resulting bond. In somecases the surfaces are treated chemically with one or more of acids,bases or plasma treatments to produce a surface that yields a weak bondwhen brought into contact with the oxide surface. Bonding is performedat elevated temperatures and elevated pressures.

In another embodiment the bonding media could be a dielectric such assilicon dioxide or silicon nitride. Such a media may be desirable wherelow conductivity is desired at the bond interface to achieve propertiessuch as reduced device capacitance to enable increased frequencyoperation. The bond media comprising the bond interface can be comprisedof many other materials such as oxide-oxide pair,semiconductor-semiconductor pair, spin-on-glass, soldering alloys,polymers, photoresists, wax, or a combination thereof.

The carrier wafer can be chosen based on any number of criteriaincluding but not limited to cost, thermal conductivity, thermalexpansion coefficients, size, electrical conductivity, opticalproperties, and processing compatibility. The patterned epitaxy wafer isprepared in such a way as to allow subsequent selective release ofbonded epitaxy regions. The patterned carrier wafer is prepared suchthat bond pads are arranged in order to enable the selective areabonding process. These wafers can be prepared by a variety of processflows, some embodiments of which are described below. In the firstselective area bond step, the epitaxy wafer is aligned with thepre-patterned bonding pads on the carrier wafer and a combination ofpressure, heat, and/or sonication is used to bond the mesas to thebonding pads.

In one embodiment of the invention the carrier wafer is anothersemiconductor material, a metallic material, or a ceramic material. Somepotential candidates include silicon, gallium arsenide, sapphire,silicon carbide, diamond, gallium nitride, AlN, polycrystalline AlN,indium phosphide, germanium, quartz, copper, copper tungsten, gold,silver, aluminum, stainless steel, or steel.

In another embodiment, the carrier wafer is selected based on size andcost. For example, ingle crystal silicon wafers are available indiameters up to 300 mm or 12 inch, and are most cost effective. Bytransferring gallium and nitrogen epitaxial materials from 2″ galliumand nitrogen containing bulk substrates to large silicon substrates of150 mm, 200 mm, or 300 mm diameter the effective area of thesemiconductor device wafer can be increases by factors of up to 36 orgreater. This feature of this invention allows for high quality galliumand nitrogen containing semiconductor devices to be fabricated in massvolume leveraging the established infrastructure in silicon foundries.

In another embodiment of the invention the carrier wafer material ischosen such that it has similar thermal expansion properties togroup-III nitrides, high thermal conductivity and is available as largearea wafers compatible with standard semiconductor device fabricationprocesses. The carrier wafer is then processed with structures enablingit to also act as the submount for the semiconductor devices.Singulation of the carrier wafers into individual die can beaccomplished either by sawing, cleaving, or a scribing and breakingprocess. By combining the functions of the carrier wafer and finishedsemiconductor device submount the number of components and operationsneeded to build a packaged device is reduced, thereby lowering the costof the final semiconductor device significantly.

In one embodiment of this invention, the bonding of the semiconductordevice epitaxial material to the carrier wafer process can be performedprior to the selective etching of the sacrificial region and subsequentrelease of the gallium and nitrogen containing substrate. FIG. 6 is aschematic illustration of a process comprised of first forming the bondbetween the gallium and nitrogen containing epitaxial material formed onthe gallium and nitrogen containing substrate and then subjecting therelease material to the PEC etch process to release the gallium andnitrogen containing substrate. In this embodiment, an epitaxial materialis deposited on the gallium and nitrogen containing substrate, such as aGaN substrate, through an epitaxial deposition process such as metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE),or other. The epitaxial material consists of at least a sacrificialrelease layer and one or more device layers. In some embodiments abuffer layer is grown on between the substrate surface region and thesacrificial release region. In FIG. 6 substrate wafer 101 is overlaid bya buffer layer 102, a selectively etchable sacrificial layer 104 and acollection of device layers 101. The bond layer 105 is deposited alongwith a cathode metal 106 that will be used to facilitate thephotoelectrochemical etch process for selectively removing thesacrificial layer.

In a preferred embodiment of this invention, the bonding process isperformed after the selective etching of the sacrificial region. Thisembodiment offers several advantages. One advantage is easier access forthe selective etchant to uniformly etch the sacrificial region acrossthe semiconductor wafer comprising a bulk gallium and nitrogencontaining substrate such as GaN and bulk gallium and nitrogencontaining epitaxial device layers. A second advantage is the ability toperform multiple bond steps. In one example, the “etch then bond”process flow can be deployed where the mesas are retained on thesubstrate by controlling the etch process such that not all of thesacrificial layer is removed. A substrate wafer 101 is overlaid by abuffer layer 102, a selectively etchable sacrificial layer 104 and acollection of device layers 101. The bond layer 105 is deposited alongwith a cathode metal 106 that will be used to facilitate thephotoelectrochemical etch process for selectively removing thesacrificial layer. The selective etch process is carried out to thepoint where only a small fraction of the sacrificial layer is remaining,such that the mesas are retained on the substrate, but the unetchedportions of the sacrificial layer are easily broken during or after themesas are bonded to the carrier wafer.

A critical challenge of the etch then bond embodiment is mechanicallysupporting the undercut epitaxial device layer mesa region fromspatially shifting prior to the bonding step. If the mesas shift theability to accurately align and arrange them to the carrier wafer willbe compromised, and hence the ability to manufacture with acceptableyields. This challenge mechanically fixing the mesa regions in placeprior to bonding can be achieved in several ways. In a preferredembodiment anchor regions are used to mechanically support the mesas tothe gallium and nitrogen containing substrate prior to the bonding stepwherein they are releases from the gallium and nitrogen containingsubstrate and transferred to the carrier wafer.

Anchor regions are special features that can be designed into the photomasks which attach the undercut device layers to the gallium andnitrogen containing substrate, but which are too large to themselves beundercut, or which due to the design of the mask contain regions wherethe sacrificial layers are not removed or these features may be composedof metals or dielectrics that are resistant to the etch. These featuresact as anchors, preventing the undercut device layers from detachingfrom the substrate and prevent the device layers from spatiallyshifting. This attachment to the substrate can also be achieved byincompletely removing the sacrificial layer, such that there is atenuous connection between the undercut device layers and the substratewhich can be broken during bonding. The surfaces of the bonding materialon the carrier wafer and the device wafer are then brought into contactand a bond is formed which is stronger than the attachment of theundercut device layers to the anchors or remaining material of thesacrificial layers. After bonding, the separation of the carrier anddevice wafers transfers the device layers to the carrier wafer.

In one embodiment the anchor region is formed by features that are widerthan the device layer mesas such that the sacrificial region in theseanchor regions is not fully removed during the undercut of the devicelayers. In one example the mesas are retained on the substrate bydeposition of an etch resistant material acting as an anchor byconnecting the mesas to the substrate. In this example a substrate waferis overlaid by a buffer layer, a selectively etchable sacrificial layerand a collection of device layers. The bond layer is deposited alongwith a cathode metal that will be used to facilitate thephotoelectrochemical etch process for selectively removing thesacrificial layer. A layer of etch resistant material, which may becomposed of metal, ceramic, polymer or a glass, is deposited such thatit connects to both the mesa and the substrate. The selective etchprocess is carried out such that the sacrificial layer is fully removedand only the etch-resistant layer connects the mesa to the substrate

In another example of anchor techniques, the mesas are retained on thesubstrate by use of an anchor composed of epitaxial material. In thisexample a substrate wafer is overlaid by a buffer layer, a selectivelyetchable sacrificial layer and a collection of device layers. The bondlayer is deposited along with a cathode metal that will be used tofacilitate the photoelectrochemical etch process for selectivelyremoving the sacrificial layer. The anchor is shaped such that duringthe etch, a small portion of the sacrificial layer remains unetched andcreates a connection between the undercut mesa and the substrate wafer.

In one embodiment the anchors are positioned either at the ends or sidesof the undercut die such that they are connected by a narrow undercutregion of material. In this example the narrow connecting material isfar from the bond metal and is design such that the undercut materialcleaves at the connecting material rather than across the die. This hasthe advantage of keeping the entire width of the die undamaged, whichwould be advantageous. In another embodiment, geometric features areadded to the connecting material to act as stress concentrators and thebond metal is extended onto the narrow connecting material. The bondmetal reinforces the bulk of the connecting material. Adding thesefeatures increases the control over where the connection will cleave.These features can be triangles, circles, rectangles or any deviationthat provides a narrowing of the connecting material or a concaveprofile to the edge of the connecting material.

In another embodiment the anchors are of small enough lateral extentthat they may be undercut, however a protective coating is used toprevent etch solution from accessing the sacrificial layers in theanchors. This embodiment is advantageous in cases when the width of thedie to be transferred is large. Unprotected anchors would need to belarger to prevent complete undercutting, which would reduce the densityof die and reduce the utilization efficiency of epitaxial material.

In another embodiment, the anchors are located at the ends of the dieand the anchors form a continuous strip of material that connects to allor a plurality of die. This configuration is advantageous since theanchors can be patterned into the material near the edge of wafers orlithographic masks where material utilization is otherwise poor. Thisallows for utilization of device material at the center of the patternto remain high even when die sizes become large.

In a preferred embodiment the anchors are formed by depositing regionsof an etch-resistant material that adheres well to the epitaxial andsubstrate material. These regions overlay a portion of the semiconductordevice layer mesa and some portion of the structure that will not beundercut during the etch such as the substrate. These regions form acontinuous connection, such that after the semiconductor device layermesa is completely undercut they provide a mechanical support preventingthe semiconductor device layer mesa from detaching from the substrate.Metal layers are then deposited on the top of semiconductor device layermesa, the sidewall of the semiconductor device layer mesa and the bottomof the etched region surrounding the mesa such that a continuousconnection is formed. As an example, the metal layers could compriseabout 20 nm of titanium to provide good adhesion and be capped withabout 500 nm of gold, but of course the choice of metal and thethicknesses could be others. In an example, the length of thesemiconductor device die sidewall coated in metal is about 1 nm to about40 nm, with the upper thickness being less than the width of thesemiconductor device die such that the sacrificial layer is etchedcompletely in the region near the metal anchor where access to thesacrificial layer by etchant will be limited.

The mesa regions can be formed by dry or wet chemical etching, and inone example would include at least a p++ GaN contact layer, a p-typecladding layer comprised of GaN, AlGaN, or InAlGaN, light emittinglayers such as quantum wells separated by barriers, waveguiding layerssuch as InGaN layers, and the one or more n-type cladding layerscomprised of GaN, AlGaN, or InAlGaN, the sacrificial layer, and aportion of the n-type GaN epitaxial layer beneath the sacrificial layer.A p-contact metal is first deposited on the p++ GaN contact layer inorder to form a high quality electrical contact with the p-typecladding. A second metal stack is then patterned and deposited on themesa, overlaying the p-contact metal. The second metal stack consists ofan n-contact metal, forming a good electrical contact with the n-typeGaN layer beneath the sacrificial layer, as well as a relatively thickmetal layer that acts as both the mesa bond pad as well as the cathodemetal. The bond/cathode metal also forms a thick layer overlaying theedge of the mesa and providing a continuous connection between the mesatop and the substrate. After the sacrificial layer is removed byselective photochemical etching the thick metal provides mechanicalsupport to retain the mesa in position on the GaN wafer until thebonding to the carrier wafer is carried out.

The use of metal anchors have several advantages over the use of anchorsmade from the epitaxial device material. The first is density of thetransferable mesas on the donor wafer containing the epitaxialsemiconductor device layers and the gallium and nitrogen containing bulksubstrate. Anchors made from the epitaxial material must be large enoughto not be fully undercut by the selective etch, or they must beprotected somehow with a passivating layer. The inclusion of a largefeature that is not transferred will reduce the density of mesas in oneor more dimensions on the epitaxial device wafer. The use of metalanchors is preferable because the anchors are made from a material thatis resistant to etch and therefore can be made with small dimensionsthat do not impact mesa density. The second advantage is that itsimplifies the processing of the mesas because a separate passivatinglayer is no longer needed to isolate the active region from the etchsolution. Removing the active region protecting layer reduces the numberof fabrication steps while also reducing the size of the mesa required.

In a particular embodiment, the cathode metal stack also includes metallayers intended to increase the strength of the metal anchors. Forexample the cathode metal stack might consist of 100 nm of Ti to promoteadhesion of the cathode metal stack and provide a good electricalcontact to the n-type cladding. The cathode metal stack could thenincorporate a layer of tungsten, which has an elastic modulus on theorder of four times higher than gold. Incorporating the tungsten wouldreduce the thickness of gold required to provide enough mechanicalsupport to retain the mesas after they are undercut by the selectiveetch.

In another embodiment of the invention the sacrificial region iscompletely removed by PEC etching and the mesa remains anchored in placeby any remaining defect pillars. PEC etching is known to leave intactmaterial around defects which act as recombination centers. Additionalmechanisms by which a mesa could remain in place after a completesacrificial etch include static forces or Van der Waals forces. In oneembodiment the undercutting process is controlled such that thesacrificial layer is not fully removed.

In a preferred embodiment, the semiconductor device epitaxy materialwith the underlying sacrificial region is fabricated into a dense arrayof mesas on the gallium and nitrogen containing bulk substrate with theoverlying semiconductor device layers. The mesas are formed using apatterning and a wet or dry etching process wherein the patterningcomprises a lithography step to define the size and pitch of the mesaregions. Dry etching techniques such as reactive ion etching,inductively coupled plasma etching, or chemical assisted ion beametching are candidate methods. Alternatively, a wet etch can be used.The etch is configured to terminate at or below the one or moresacrificial region below the device layers. This is followed by aselective etch process such as PEC to fully or partially etch theexposed sacrificial region such that the mesas are undercut. Thisundercut mesa pattern pitch will be referred to as the ‘first pitch’.The first pitch is often a design width that is suitable for fabricatingeach of the epitaxial regions on the substrate, while not large enoughfor the desired completed semiconductor device design, which oftendesire larger non-active regions or regions for contacts and the like.For example, these mesas would have a first pitch ranging from about 5microns to about 500 microns or to about 5000 microns. Each of thesemesas is a ‘die’.

In a preferred embodiment, these die are transferred to a carrier waferat a second pitch using a selective bonding process such that the secondpitch on the carrier wafer is greater than the first pitch on thegallium and nitrogen containing substrate. In this embodiment the dieare on an expanded pitch for so called “die expansion”. In an example,the second pitch is configured with the die to allow each die with aportion of the carrier wafer to be a semiconductor device, includingcontacts and other components. For example, the second pitch would beabout 50 microns to about 1000 microns or to about 5000 microns, butcould be as large at about 3-10 mm or greater in the case where a largesemiconductor device chip is required for the application. The largersecond pitch could enable easier mechanical handling without the expenseof the costly gallium and nitrogen containing substrate and epitaxialmaterial, allow the real estate for additional features to be added tothe semiconductor device chip such as bond pads that do not require thecostly gallium and nitrogen containing substrate and epitaxial material,and/or allow a smaller gallium and nitrogen containing epitaxial wafercontaining epitaxial layers to populate a much larger carrier wafer forsubsequent processing for reduced processing cost. For example, a 4 to 1die expansion ratio would reduce the density of the gallium and nitrogencontaining material by a factor of 4, and hence populate an area on thecarrier wafer 4 times larger than the gallium and nitrogen containingsubstrate. This would be equivalent to turning a 2″ gallium and nitrogensubstrate into a 4″ carrier wafer. In particular, the present inventionincreases utilization of substrate wafers and epitaxy material through aselective area bonding process to transfer individual die of epitaxymaterial to a carrier wafer in such a way that the die pitch isincreased on the carrier wafer relative to the original epitaxy wafer.The arrangement of epitaxy material allows device components which donot require the presence of the expensive gallium and nitrogencontaining substrate and overlying epitaxy material often fabricated ona gallium and nitrogen containing substrate to be fabricated on thelower cost carrier wafer, allowing for more efficient utilization of thegallium and nitrogen containing substrate and overlying epitaxymaterial.

FIG. 7 is a schematic representation of the die expansion process withselective area bonding according to the present invention. A devicewafer is prepared for bonding in accordance with an embodiment of thisinvention. The wafer consists of a substrate 106, buffer layers 103, thefully removed sacrificial layer 109, the device layers 102, the bondingmedia 101, the cathode metal utilized in the PEC etch removal of thesacrificial layer and the anchor material 104. The mesa regions formedin the gallium and nitrogen containing epitaxial wafer form dice ofepitaxial material and release layers defined through processing.Individual epitaxial material die are formed at first pitch. A carrierwafer is prepared consisting of the carrier wafer 107 and bond pads 108at second pitch. The substrate is aligned to the carrier wafer such thata subset of the mesa on the gallium and nitrogen containing substratewith a first pitch align with a subset of bond pads on the carrier at asecond pitch. Since the first pitch is greater than the second pitch andthe mesas will comprise device die, the basis for die expansion isestablished. The bonding process is carried out and upon separation ofthe substrate from the carrier wafer the subset of mesas are selectivelytransferred to the carrier. The process is then repeated with a secondset of mesas and bond pads on the carrier wafer until the carrier waferis populated fully by epitaxial mesas. The gallium and nitrogencontaining epitaxy substrate 201 can now optionally be prepared forreuse.

In the example depicted in FIG. 7, one quarter of the epitaxial die aretransferred in this first selective bond step, leaving three quarters onthe epitaxy wafer. The selective area bonding step is then repeated totransfer the second quarter, third quarter, and fourth quarter of theepitaxial die to the patterned carrier wafer. This selective area bondmay be repeated any number of times and is not limited to the four stepsdepicted in FIG. 7. The result is an array of epitaxial die on thecarrier wafer with a wider die pitch than the original die pitch on theepitaxy wafer. The die pitch on the epitaxial wafer will be referred toas pitch 1, and the die pitch on the carrier wafer will be referred toas pitch 2, where pitch 2 is greater than pitch 1.

In one embodiment the bonding between the carrier wafer and the galliumand nitrogen containing substrate with epitaxial layers is performedbetween bonding layers that have been applied to the carrier and thegallium and nitrogen containing substrate with epitaxial layers. Thebonding layers can be a variety of bonding pairs including metal-metal,oxide-oxide, soldering alloys, photoresists, polymers, wax, etc. Onlyepitaxial die which are in contact with a bond bad on the carrier waferwill bond. Sub-micron alignment tolerances are possible on commercialdie bonders. The epitaxy wafer is then pulled away, breaking the epitaxymaterial at a weakened epitaxial release layer such that the desiredepitaxial layers remain on the carrier wafer. Herein, a ‘selective areabonding step’ is defined as a single iteration of this process.

In one embodiment, the carrier wafer is patterned in such a way thatonly selected mesas come in contact with the metallic bond pads on thecarrier wafer. When the epitaxy substrate is pulled away the bondedmesas break off at the weakened sacrificial region, while the un-bondedmesas remain attached to the epitaxy substrate. This selective areabonding process can then be repeated to transfer the remaining mesas inthe desired configuration. This process can be repeated through anynumber of iterations and is not limited to the two iterations depictedin FIG. 3a . The carrier wafer can be of any size, including but notlimited to about 2 inch, 3 inch, 4 inch, 6 inch, 8 inch, and 12 inch.After all desired mesas have been transferred, a second bandgapselective PEC etch can be optionally used to remove any remainingsacrificial region material to yield smooth surfaces. At this pointstandard semiconductor device processes can be carried out on thecarrier wafer. Another embodiment of the invention incorporates thefabrication of device components on the dense epitaxy wafers before theselective area bonding steps.

In an example, the present invention provides a method for increasingthe number of gallium and nitrogen containing semiconductor deviceswhich can be fabricated from a given epitaxial surface area; where thegallium and nitrogen containing epitaxial layers overlay gallium andnitrogen containing substrates. The gallium and nitrogen containingepitaxial material is patterned into die with a first die pitch; the diefrom the gallium and nitrogen containing epitaxial material with a firstpitch is transferred to a carrier wafer to form a second die pitch onthe carrier wafer; the second die pitch is larger than the first diepitch.

In an example, each epitaxial device die is an etched mesa with a pitchof between about 1 μm and about 100 μm wide or between about 100 micronand about 500 microns wide or between about 500 micron and about 3000microns wide and between about 100 and about 3000 μm long. In anexample, the second die pitch on the carrier wafer is between about 100microns and about 200 microns or between about 200 microns and about1000 microns or between about 1000 microns and about 3000 microns. In anexample, the second die pitch on the carrier wafer is between about 2times and about 50 times larger than the die pitch on the epitaxy wafer.In an example, semiconductor LED devices, laser devices, or electronicdevices are fabricated on the carrier wafer after epitaxial transfer. Inan example, the semiconductor devices contain GaN, AlN, InN, InGaN,AlGaN, InAlN, and/or InAlGaN. In an example, the gallium and nitrogencontaining material are grown on a polar, nonpolar, or semipolar plane.In an example, one or multiple semiconductor devices are fabricated oneach die of epitaxial material. In an example, device components, whichdo not require epitaxy material are placed in the space between epitaxydie.

In one embodiment, device dice are transferred to a carrier wafer suchthat the distance between die is expanded in both the transverse as wellas lateral directions. This can be achieved by spacing bond pads on thecarrier wafer with larger pitches than the spacing of device die on thesubstrate.

In another embodiment of the invention device dice from a plurality ofepitaxial wafers are transferred to the carrier wafer such that eachdesign width on the carrier wafer contains dice from a plurality ofepitaxial wafers. When transferring die at close spacings from multipleepitaxial wafers, it is important for the un-transferred die on theepitaxial wafer to not inadvertently contact and bond to die alreadytransferred to the carrier wafer. To achieve this, die from a firstepitaxial wafer are transferred to a carrier wafer using the methodsdescribed above. A second set of bond pads are then deposited on thecarrier wafer and are made with a thickness such that the bondingsurface of the second pads is higher than the top surface of the firstset of transferred die. This is done to provide adequate clearance forbonding of the die from the second epitaxial wafer. A second substratetransfer a second set of die to the carrier. Finally, the semiconductordevices are fabricated and passivation layers are deposited followed byelectrical contact layers that allow each dice to be individuallydriven. The die transferred from the first and second substrates arespaced at a pitch which is smaller than the second pitch of the carrierwafer. This process can be extended to transfer of die from any numberof substrates, and to the transfer of any number of devices per dicefrom each substrate.

An example of an epitaxial structure for a laser diode device accordingto this invention is shown in FIG. 8. In this embodiment, an n-GaNbuffer layer followed by a sacrificial layer is grown along with ann-contact layer that will be exposed after transfer. Overlaying then-contact layer are n-cladding layers, an n-side separate confinementheterostructure (n-SCH) layer, an active region, a p-side separateconfinement heterostructure (p-SCH) layer, a p-cladding layer, and ap-contact region. In one example of this embodiment an n-type GaN bufferlayer is grown on a c-plane oriented, bulk-GaN wafer. In another examplethe substrate is comprised of a semipolar or nonpolar orientation.Overlaying the buffer layer is a sacrificial layer comprised by InGaNwells separated by GaN barriers with the well composition and thicknesschosen to result in the wells absorbing light at wavelengths shorterthan 450 nm, though in some embodiments the absorption edge would be asshort as 400 nm and in other embodiments as long as 520 nm. Overlayingthe sacrificial layer is an n-type contact layer consisting of GaN dopedwith silicon at a concentration of 5E18 cm-3, but can be other dopinglevels in the range between 5E17 and 1E19 cm-3. Overlaying the contactlayer is an n-type cladding layer comprised of GaN or AlGaN layer with athickness of 1 micron with an average composition of 4% AlN, though inother embodiments the thickness may range from 0.25 to 2 microns with anaverage composition of 0-8% AlN. Overlaying the n-cladding is an n-typewave-guiding or separate confinement heterostructure (SCH) layer thathelps provide index contrast with the cladding to improve confinement ofthe optical modes. The nSCH is InGaN with a composition of 4% InN andhas a thickness of 100 nm, though in other embodiments the InGaN nSCHmay range from 20 to 300 nm in thickness and from 0-8% InN and may becomposed of several layers of varying composition and thickness.Overlaying the n-SCH are light emitting quantum well layers consistingof two 3.5 nm thick In_(0.15)Ga_(0.85)N quantum wells separated by 4 nmthick GaN barriers, though in other embodiments there may 1 to 7 lightemitting quantum well layers consisting of 1 nm to 6 nm thick quantumwells separated by GaN or InGaN barriers of 1 nm to 25 nm thick.Overlaying the light emitting layers is an optional InGaN pSCH with acomposition of 4% InN and has a thickness of 100 nm, though in otherembodiments the nSCH may range from 20 to 300 nm in thickness and from0-8% InN and may be composed of several layers of varying compositionand thickness. Overlaying the pSCH is an optional AlGaN electronblocking layer [EBL] with a composition of 10% AlN, though in otherembodiments the AlGaN EBL composition may range from 0% to 30% AlN.Overlaying the EBL a p-type cladding comprised of GaN or AlGaN layerwith a thickness of 0.8 micron with an average composition of 4% AlN,though in other embodiments the thickness may range from 0.25 to 2microns with an average composition of 0-8% AlN. The p-cladding isterminated at the free surface of the crystal with a highly doped p++ orp-contact layer that enables a high quality electrical p-type contact tothe device.

Once the laser diode epitaxial structure has been transferred to thecarrier wafer as described in this invention, wafer level processing canbe used to fabricate the die into laser diode devices. The wafer processsteps may be similar to those described in this specification for moreconventional laser diodes. For example, in many embodiments the bondingmedia and die will have a total thickness of less than about 7 microns,making it possible to use standard photoresist, photoresist dispensingtechnology and contact and projection lithography tools and techniquesto pattern the wafers. The aspect ratios of the features are compatiblewith deposition of thin films, such as metal and dielectric layers,using evaporators, sputter and CVD deposition tools.

The laser diode device may have laser stripe region formed in thetransferred gallium and nitrogen containing epitaxial layers. In thecase where the laser is formed on a polar c-plane, the laser diodecavity can be aligned in the m-direction with cleaved or etched mirrors.Alternatively, in the case where the laser is formed on a semipolarplane, the laser diode cavity can be aligned in a projection of ac-direction. The laser strip region has a first end and a second end andis formed on a gallium and nitrogen containing substrate having a pairof cleaved mirror structures, which face each other. The first cleavedfacet comprises a reflective coating and the second cleaved facetcomprises no coating, an antireflective coating, or exposes gallium andnitrogen containing material. The first cleaved facet is substantiallyparallel with the second cleaved facet. The first and second cleavedfacets are provided by a scribing and breaking process according to anembodiment or alternatively by etching techniques using etchingtechnologies such as reactive ion etching (RIE), inductively coupledplasma etching (ICP), or chemical assisted ion beam etching (CAIBE), orother method. Typical gases used in the etching process may include Cland/or BCl3. The first and second mirror surfaces each comprise areflective coating. The coating is selected from silicon dioxide,hafnia, and titania, tantalum pentoxide, zirconia, includingcombinations, and the like. Depending upon the design, the mirrorsurfaces can also comprise an anti-reflective coating.

In a specific embodiment, the method of facet formation includessubjecting the substrates to a laser for pattern formation. In apreferred embodiment, the pattern is configured for the formation of apair of facets for one or more ridge lasers. In a preferred embodiment,the pair of facets facet each other and are in parallel alignment witheach other. In a preferred embodiment, the method uses a UV (355 nm)laser to scribe the laser bars. In a specific embodiment, the laser isconfigured on a system, which allows for accurate scribe linesconfigured in one or more different patterns and profiles. In one ormore embodiments, the laser scribing can be performed on the back-side,front-side, or both depending upon the application. Of course, there canbe other variations, modifications, and alternatives.

In a specific embodiment, the method uses backside laser scribing or thelike. With backside laser scribing, the method preferably forms acontinuous line laser scribe that is perpendicular to the laser bars onthe backside of the GaN substrate. In a specific embodiment, the laserscribe is generally about 15-20 um deep or other suitable depth.Preferably, backside scribing can be advantageous. That is, the laserscribe process does not depend on the pitch of the laser bars or otherlike pattern. Accordingly, backside laser scribing can lead to a higherdensity of laser bars on each substrate according to a preferredembodiment. In a specific embodiment, backside laser scribing, however,may lead to residue from the tape on one or more of the facets. In aspecific embodiment, backside laser scribe often requires that thesubstrates face down on the tape. With front-side laser scribing, thebackside of the substrate is in contact with the tape. Of course, therecan be other variations, modifications, and alternatives.

It is well known that etch techniques such as chemical assisted ion beametching (CAIBE), inductively coupled plasma (ICP) etching, or reactiveion etching (RIE) can result in smooth and vertical etched sidewallregions, which could serve as facets in etched facet laser diodes. Inthe etched facet process a masking layer is deposited and patterned onthe surface of the wafer. The etch mask layer could be comprised ofdielectrics such as silicon dioxide (SiO2), silicon nitride (SixNy), acombination thereof or other dielectric materials. Further, the masklayer could be comprised of metal layers such as Ni or Cr, but could becomprised of metal combination stacks or stacks comprising metal anddielectrics. In another approach, photoresist masks can be used eitheralone or in combination with dielectrics and/or metals. The etch masklayer is patterned using conventional photolithography and etch steps.The alignment lithography could be performed with a contact aligner orstepper aligner. Such lithographically defined mirrors provide a highlevel of control to the design engineer. After patterning of thephotoresist mask on top of the etch mask is complete, the patterns inthen transferred to the etch mask using a wet etch or dry etchtechnique. Finally, the facet pattern is then etched into the waferusing a dry etching technique selected from CAIBE, ICP, RIE and/or othertechniques. The etched facet surfaces must be highly vertical of betweenabout 87 and about 93 degrees or between about 89 and about 91 degreesfrom the surface plane of the wafer. The etched facet surface regionmust be very smooth with root mean square roughness values of less thanabout 50 nm, 20 nm, 5 nm, or 1 nm. Lastly, the etched must besubstantially free from damage, which could act as nonradiativerecombination centers and hence reduce the COMD threshold. CAIBE isknown to provide very smooth and low damage sidewalls due to thechemical nature of the etch, while it can provide highly vertical etchesdue to the ability to tilt the wafer stage to compensate for anyinherent angle in etch.

The laser stripe is characterized by a length and width. The lengthranges from about 50 microns to about 3000 microns, but is preferablybetween about 10 microns and about 400 microns, between about 400microns and about 800 microns, or about 800 microns and about 1600microns, but could be others. The stripe also has a width ranging fromabout 0.5 microns to about 50 microns, but is preferably between about0.8 microns and about 2.5 microns for single lateral mode operation orbetween about 2.5 um and about 35 um for multi-lateral mode operation,but can be other dimensions. In a specific embodiment, the presentdevice has a width ranging from about 0.5 microns to about 1.5 microns,a width ranging from about 1.5 microns to about 3.0 microns, a widthranging from about 3.0 microns to about 35 microns, and others. In aspecific embodiment, the width is substantially constant in dimension,although there may be slight variations. The width and length are oftenformed using a masking and etching process, which are commonly used inthe art.

The laser stripe is provided by an etching process selected from dryetching or wet etching. The device also has an overlying dielectricregion, which exposes a p-type contact region. Overlying the contactregion is a contact material, which may be metal or a conductive oxideor a combination thereof. The p-type electrical contact may be depositedby thermal evaporation, electron beam evaporation, electroplating,sputtering, or another suitable technique. Overlying the polished regionof the substrate is a second contact material, which may be metal or aconductive oxide or a combination thereof and which comprises the n-typeelectrical contact. The n-type electrical contact may be deposited bythermal evaporation, electron beam evaporation, electroplating,sputtering, or another suitable technique.

An example of a processed laser diode cross-section according to oneembodiment of the present invention is shown in FIG. 9. In this examplean n-contact 201 is formed on top of n-type gallium and nitrogen contactlayer 202 and n-type cladding layer 203 that have been etched to form aridge waveguide 204. The n-type cladding layer 203 overlies an n-sidewaveguide layer or separate confinement hetereostructure (SCH) layer 205and the n-side SCH overlies an active region 206 that contains lightemitting layers such as quantum wells. The active region overlies anoptional p-side SCH layer 207 and an electron blocking layer (EBL) 208.The optional p-side SCH layer overlies the p-type cladding 209 and ap-contact layer 210. Underlying the p-contact layer 210 is a metal stack211 that contains the p-type contact and bond metal used to attach thetransferred gallium and nitrogen containing epitaxial layers to thecarrier wafer 212.

Once the lasers have been fully processed within the gallium andnitrogen containing layers that have been transferred to the carrierwafer, the carrier wafer must be diced. Several techniques can be usedto dice the carrier wafer and the optimal process will depend on thematerial selection for the carrier wafer. As an example, for Si, InP, orGaAs carrier wafers that cleave very easily, a cleaving process can beused wherein a scribing and breaking process using conventional diamondscribe techniques may be most suitable. For harder materials such asGaN, AlN, SiC, sapphire, or others where cleaving becomes more difficulta laser scribing and breaking technique may be most suitable. In otherembodiments a sawing process may be the most optimal way to dice thecarrier wafer into individual laser chips. In a sawing process a rapidlyrotating blade with hard cutting surfaces like diamond are used,typically in conjunction with spraying water to cool and lubricate theblade. Example saw tools used to commonly dice wafers include Disco sawsand Accretech saws.

By choosing a carrier wafer material such as AlN, BeO, diamond, or SiCthat is suitable as a submount between the laser chip and the mountingsurface, the diced laser chip on the carrier wafer is in itself a chipon submount (CoS). This wafer level packaging features is a strongbenefit of the lifted-off and transferred gallium and nitrogencontaining epitaxial layer embodiment of this invention. The submountcan be the common support member wherein the phosphor member of the CPoSwould also be attached. Alternatively, the submount can be anintermediate submount intended to be mounted to the common supportmember wherein the phosphor material is attached. The submount member ischaracterized by a width, length, and thickness. In one example whereinthe submount is the common support member for the phosphor and the laserdiode, the submount would likely have a length ranging in dimension fromabout 0.5 mm to about 3 mm or about 5 mm, a width ranging from about 0.3mm to about 1 mm or from about 1 mm to 3 mm, and a thickness from about200 um to about 1 mm. In tan example wherein the submount is anintermediate submount between the laser diode and the common supportmember it may be characterized by length ranging in dimension from about0.5 mm to about 2 mm, a width ranging from about 150 um to about 1 mm,and the thickness may ranging from about 50 um to about 500 um.

A schematic diagram illustrating a CoS based on lifted off andtransferred epitaxial gallium and nitrogen containing layers accordingto this present invention is shown in FIG. 10. The CoS is comprised ofsubmount material 201 configured from the carrier wafer with thetransferred epitaxial material with a laser diode configured within theepitaxy 202. Electrodes 203 and 204 are electrically coupled to then-side and the p-side of the laser diode device and configured totransmit power from an external source to the laser diode to generate alaser beam output 205 from the laser diode. The electrodes areconfigured for an electrical connection to an external power source suchas a laser driver, a current source, or a voltage source. Wirebonds canbe formed on the electrodes to couple the power to the laser diodedevice. This integrated CoS device with transferred epitaxial materialoffers advantages over the conventional configuration illustrated inFIG. 4 such as size, cost, and performance due to the low thermalimpedance.

Further process and device description for this embodiment describinglaser diodes formed in gallium and nitrogen containing epitaxial layersthat have been transferred from the native gallium and nitrogencontaining substrates are described in U.S. patent application Ser. No.14/312,427 and U.S. Patent Publication No. 2015/0140710, which areincorporated by reference herein. As an example, this technology of GaNtransfer can enable lower cost, higher performance, and a more highlymanufacturable process flow.

In this embodiment, the carrier wafer can be selected to provide anideal submount material for the integrated CPoS white light source. Thatis, the carrier wafer serving as the laser diode submount would alsoserve as the common support member for the laser diode and the phosphorto enable an ultra-compact CPoS integrated white light source. In oneexample, the carrier wafer is formed from silicon carbide (SiC). SiC isan ideal candidate due to its high thermal conductivity, low electricalconductivity, high hardness and robustness, and wide availability. Inother examples AlN, diamond, GaN, InP, GaAs, or other materials can beused as the carrier wafer and resulting submount for the CPoS. In oneexample, the laser chip is diced out such that there is an area in frontof the front laser facet intended for the phosphor. The phosphormaterial would then be bonded to the carrier wafer and configured forlaser excitation according to this embodiment.

After fabrication of the laser diode on a submount member, in one ormore embodiments of this invention the construction of the integratedwhite source would proceed to integration of the phosphor with the laserdiode and common support member. Phosphor selection is a keyconsideration within the laser based integrated white light source. Thephosphor must be able to withstand the extreme optical intensity andassociated heating induced by the laser excitation spot without severedegradation. Important characteristics to consider for phosphorselection include;

-   -   A high conversion efficiency of optical excitation power to        white light lumens. In the example of a blue laser diode        exciting a yellow phosphor, a conversion efficiency of over 150        lumens per optical watt, or over 200 lumens per optical watt, or        over 300 lumens per optical watt is desired.    -   A high optical damage threshold capable of withstanding 1-20 W        of laser power in a spot comprising a diameter of 1 mm, 500 um,        200 um, 100 um, or even 50 um.    -   High thermal damage threshold capable of withstanding        temperatures of over 150° C., over 200° C., or over 300° C.        without decomposition.    -   A low thermal quenching characteristic such that the phosphor        remains efficient as it reaches temperatures of over 150° C.,        200° C., or 250° C.    -   A high thermal conductivity to dissipate the heat and regulate        the temperature. Thermal conductivities of greater than 3 W/mK,        greater than 5 W/mK, greater than 10 W/mKm, and even greater        than 15 W/mK are desirable.    -   A proper phosphor emission color for the application    -   A suitable porosity characteristic that leads to the desired        scattering of the coherent excitation without unacceptable        reduction in thermal conductivity or optical efficiency.    -   A proper form factor for the application. Such form factors        include, but are not limited to blocks, plates, disks, spheres,        cylinders, rods, or a similar geometrical element. Proper choice        will be dependent on whether phosphor is operated in        transmissive or reflective mode and on the absorption length of        the excitation light in the phosphor.    -   A surface condition optimized for the application. In an        example, one or more of the phosphor surfaces can be        intentionally roughened for improved light extraction.

In a preferred embodiment, a blue laser diode operating in the 420 nm to480 nm wavelength range would be combined with a phosphor materialproviding a yellowish emission in the 560 nm to 580 nm range such thatwhen mixed with the blue emission of the laser diode a white light isproduced. For example, to meet a white color point on the black bodyline the energy of the combined spectrum may be comprised of about 30%from the blue laser emission and about 70% from the yellow phosphoremission. In other embodiments phosphors with red, green, yellow, andeven blue emission can be used in combination with the laser diodeexcitation sources in the violet, ultra-violet, or blue wavelength rangeto produce a white light with color mixing. Although such white lightsystems may be more complicated due to the use of more than one phosphormember, advantages such as improved color rendering could be achieved.

In an example, the light emitted from the one or more laser diodes ispartially converted by the phosphor element. In an example, thepartially converted light emitted generated in the phosphor elementresults in a color point, which is white in appearance. In an example,the color point of the white light is located on the Planckian blackbodylocus of points. In an example, the color point of the white light islocated within du′v′ of less than 0.010 of the Planckian blackbody locusof points. In an example, the color point of the white light ispreferably located within du′v′ of less than 0.03 of the Planckianblackbody locus of points.

The phosphor material can be operated in a transmissive mode, areflective mode, or a combination of a transmissive mode and reflectivemode, or other modes. The phosphor material is characterized by aconversion efficiency, a resistance to thermal damage, a resistance tooptical damage, a thermal quenching characteristic, a porosity toscatter excitation light, and a thermal conductivity. In a preferredembodiment the phosphor material is comprised of a yellow emitting YAGmaterial doped with Ce with a conversion efficiency of greater than 100lumens per optical watt, greater than 200 lumens per optical watt, orgreater than 300 lumens per optical watt, and can be a polycrystallineceramic material or a single crystal material.

In some embodiments of the present invention, the environment of thephosphor can be independently tailored to result in high efficiency withlittle or no added cost. Phosphor optimization for laser diodeexcitation can include high transparency, scattering or non-scatteringcharacteristics, and use of ceramic phosphor plates. Decreasedtemperature sensitivity can be determined by doping levels. A reflectorcan be added to the backside of a ceramic phosphor, reducing loss. Thephosphor can be shaped to increase in-coupling, increase outcoupling,and/or reduce back reflections. Surface roughening is a well-known meansto increase extraction of light from a solid material. Coatings,mirrors, or filters can be added to the phosphors to reduce the amountof light exiting the non-primary emission surfaces, to promote moreefficient light exit through the primary emission surface, and topromote more efficient in-coupling of the laser excitation light. Ofcourse, there can be additional variations, modifications, andalternatives.

In some embodiments, certain types of phosphors will be best suited inthis demanding application with a laser excitation source. As anexample, a ceramic yttrium aluminum garnets (YAG) doped with Ce3+ ions,or YAG based phosphors can be ideal candidates. They are doped withspecies such as Ce to achieve the proper emission color and are oftencomprised of a porosity characteristic to scatter the excitation sourcelight, and nicely break up the coherence in laser excitation. As aresult of its cubic crystal structure the YAG:Ce can be prepared as ahighly transparent single crystal as well as a polycrystalline bulkmaterial. The degree of transparency and the luminescence are dependingon the stoichiometric composition, the content of dopant, and entireprocessing and sintering route. The transparency and degree ofscattering centers can be optimized for a homogenous mixture of blue andyellow light. The YAG:CE can be configured to emit a green emission. Insome embodiments the YAG can be doped with Eu to emit a red emission.

In a preferred embodiment according to this invention, the white lightsource is configured with a ceramic polycrystalline YAG:Ce phosphorscomprising an optical conversion efficiency of greater than 100 lumensper optical excitation watt, of greater than 200 lumens per opticalexcitation watt, or even greater than 300 lumens per optical excitationwatt. Additionally, the ceramic YAG:Ce phosphors is characterized by atemperature quenching characteristics above 150° C., above 200° C., orabove 250° C. and a high thermal conductivity of 5-10 W/mK toeffectively dissipate heat to a heat sink member and keep the phosphorat an operable temperature.

In another preferred embodiment according to this invention, the whitelight source is configured with a single crystal phosphor (SCP) such asYAG:Ce. In one example the Ce:Y3Al5O12 SCP can be grown by theCzochralski technique. In this embodiment according the presentinvention the SCP based on YAG:Ce is characterized by an opticalconversion efficiency of greater than 100 lumens per optical excitationwatt, of greater than 200 lumens per optical excitation watt, or evengreater than 300 lumens per optical excitation watt. Additionally, thesingle crystal YAG:Ce phosphors is characterized by a temperaturequenching characteristics above 150° C., above 200° C., or above 300° C.and a high thermal conductivity of 8-20 W/mK to effectively dissipateheat to a heat sink member and keep the phosphor at an operabletemperature. In addition to the high thermal conductivity, high thermalquenching threshold, and high conversion efficiency, the ability toshape the phosphors into tiny forms that can act as ideal “point”sources when excited with a laser is an attractive feature.

In some embodiments the YAG:CE can be configured to emit a yellowemission. In alternative or the same embodiments a YAG:CE can beconfigured to emit a green emission. In yet alternative or the sameembodiments the YAG can be doped with Eu to emit a red emission. Inalternative embodiments, silicon nitrides or aluminum-oxi-nitrides canbe used as the crystal host materials for red, green, yellow, or blueemissions.

In one embodiment of the present invention the phosphor materialcontains a yttrium aluminum garnet host material and a rare earth dopingelement, and others. In an example, the wavelength conversion element isa phosphor which contains a rare earth doping element, selected from oneor more of Ce, Nd, Er, Yb, Ho, Tm, Dy and Sm, combinations thereof, andthe like. In an example, the phosphor material is a high-densityphosphor element. In an example, the high-density phosphor element has adensity greater than 90% of pure host crystal. Cerium (III)-doped YAG(YAG:Ce3+, or Y3Al5O12:Ce3+) can be used wherein the phosphor absorbsthe light from the blue laser diode and emits in a broad range fromgreenish to reddish, with most of output in yellow. This yellow emissioncombined with the remaining blue emission gives the “white” light, whichcan be adjusted to color temperature as warm (yellowish) or cold(blueish) white. The yellow emission of the Ce3+:YAG can be tuned bysubstituting the cerium with other rare earth elements such as terbiumand gadolinium and can even be further adjusted by substituting some orall of the aluminum in the YAG with gallium.

In alternative examples, various phosphors can be applied to thisinvention, which include, but are not limited to organic dyes,conjugated polymers, semiconductors such as AlInGaP or InGaN, yttriumaluminum garnets (YAGs) doped with Ce3+ ions(Y1-aGda)3(Al1-bGab)5O12:Ce3+, SrGa2S4:Eu2+, SrS:Eu2+, terbium aluminumbased garnets (TAGs) (Tb3Al5O5), colloidal quantum dot thin filmscontaining CdTe, ZnS, ZnSe, ZnTe, CdSe, or CdTe.

In further alternative examples, some rare-earth doped Sialons can serveas phosphors. Europium(II)-doped β-SiAlON absorbs in ultraviolet andvisible light spectrum and emits intense broadband visible emission. Itsluminance and color does not change significantly with temperature, dueto the temperature-stable crystal structure. In an alternative example,green and yellow SiAlON phosphor and a red CaAlSiN3-based (CASN)phosphor may be used.

In yet a further example, white light sources can be made by combiningnear ultraviolet emitting laser diodes with a mixture of high efficiencyeuropium based red and blue emitting phosphors plus green emittingcopper and aluminium doped zinc sulfide (ZnS:Cu,Al).

In an example, a phosphor or phosphor blend can be selected from one ormore of (Y, Gd, Tb, Sc, Lu, La).sub.3(Al, Ga,In).sub.5O.sub.12:Ce.sup.3+, SrGa.sub.2S.sub.4:Eu.sup.2+, SrS:Eu.sup.2+,and colloidal quantum dot thin films comprising CdTe, ZnS, ZnSe, ZnTe,CdSe, or CdTe. In an example, a phosphor is capable of emittingsubstantially red light, wherein the phosphor is selected from one ormore of the group consisting of (Gd,Y,Lu,La).sub.2O.sub.3:Eu.sup.3+,Bi.sup.3+; (Gd,Y,Lu,La).sub.2O.sub.2S:Eu.sup.3+, Bi.sup.3+;(Gd,Y,Lu,La)VO.sub.4:Eu.sup.3+, Bi.sup.3+; Y.sub.2(O,S).sub.3:Eu.sup.3+; Ca.sub.1-xMo.sub.1-ySi.sub.yO.sub.4: where0.05.ltoreq.x.ltoreq.0.5, 0.ltoreq.y.ltoreq.0.1;(Li,Na,K).sub.5Eu(W,Mo)O.sub.4; (Ca,Sr)S:Eu.sup.2+;SrY.sub.2S.sub.4:Eu.sup.2+; CaLa.sub.2S.sub.4:Ce.sup.3+;(Ca,Sr)S:Eu.sup.2+; 3.5MgO*0.5MgF.sub.2*GeO.sub.2:Mn.sup.4+(MFG);(Ba,Sr,Ca)Mg.sub.xP.sub.2O.sub.7:Eu.sup.2+, Mn.sup.2+; (Y,Lu).sub.2WO.sub.6:Eu.sup.3+, Mo.sup.6+;(Ba,Sr,Ca).sub.3Mg.sub.xSi.sub.2O.sub.8:Eu.sup.2+, Mn.sup.2+, wherein1<x.ltoreq.2;(RE.sub.1-yCe.sub.y)Mg.sub.2-xLi.sub.xSi.sub.3-xPxO.sub.12, where RE isat least one of Sc, Lu, Gd, Y, and Tb, 0.0001<x<0.1 and 0.001<y<0.1; (Y,Gd, Lu, La).sub.2-xEu.sub.xW.sub.1-yMo.sub.yO.sub.6, where0.5.ltoreq.x.ltoreq.1.0, 0.01.ltoreq.y.ltoreq.1.0;(SrCa).sub.1-xEu.sub.xSi.sub.5N.sub.8, where 0.01.ltoreq.x.ltoreq.0.3;SrZnO.sub.2:Sm.sup.+3; M.sub.mO.sub.nX, wherein M is selected from thegroup of Sc, Y, a lanthanide, an alkali earth metal and mixturesthereof; X is a halogen; 1.ltoreq.m.ltoreq.3; and 1.ltoreq.n.ltoreq.4,and wherein the lanthanide doping level can range from 0.1 to 40%spectral weight; and Eu.sup.3+ activated phosphate or borate phosphors;and mixtures thereof. Further details of other phosphor species andrelated techniques can be found in U.S. Pat. No. 8,956,894, in the nameof Raring et al. issued Feb. 17, 2015, and titled White light devicesusing non-polar or semipolar gallium containing materials and phosphors,which is commonly owned, and hereby incorporated by reference herein.

In some embodiments of the present invention, ceramic phosphor materialsare embedded in a binder material such as silicone. This configurationis typically less desirable because the binder materials often have poorthermal conductivity, and thus get very hot wherein the rapidly degradeand even burn. Such “embedded” phosphors are often used in dynamicphosphor applications such as color wheels where the spinning wheelcools the phosphor and spreads the excitation spot around the phosphorin a radial pattern.

Sufficient heat dissipation from the phosphor is a critical designconsideration for the integrated white light source based on laser diodeexcitation. Specifically, the optically pumped phosphor system hassources of loss in the phosphor that result is thermal energy and hencemust be dissipated to a heat-sink for optimal performance. The twoprimary sources of loss are the Stokes loss which is a result ofconverting photons of higher energy to photons of lower energy such thatdifference in energy is a resulting loss of the system and is dissipatedin the form of heat. Additionally, the quantum efficiency or quantumyield measuring the fraction of absorbed photons that are successfullyre-emitted is not unity such that there is heat generation from otherinternal absorption processes related to the non-converted photons.Depending on the excitation wavelength and the converted wavelength, theStokes loss can lead to greater than 10%, greater than 20%, and greaterthan 30%, and greater loss of the incident optical power to result inthermal power that must be dissipated. The quantum losses can lead to anadditional 10%, greater than 20%, and greater than 30%, and greater ofthe incident optical power to result in thermal power that must bedissipated. With laser beam powers in the 1 W to 100 W range focused tospot sizes of less than 1 mm in diameter, less than 500 microns indiameter, or even less than 100 microns in diameter, power densities ofover 1 W/mm2, 100 W/mm2, or even over 2,500 W/mm2 can be generated. Asan example, assuming that the spectrum is comprised of 30% of the bluepump light and 70% of the converted yellow light and a best casescenario on Stokes and quantum losses, we can compute the dissipatedpower density in the form of heat for a 10% total loss in the phosphorat 0.1 W/mm2, 10 W/mm2, or even over 250 W/mm2. Thus, even for this bestcase scenario example, this is a tremendous amount of heat to dissipate.This heat generated within the phosphor under the high intensity laserexcitation can limit the phosphor conversion performance, color quality,and lifetime.

For optimal phosphor performance and lifetime, not only should thephosphor material itself have a high thermal conductivity, but it shouldalso be attached to the submount or common support member with a highthermal conductivity joint to transmit the heat away from the phosphorand to a heat-sink. In this invention, the phosphor is either attachedto the common support member as the laser diode as in the CPoS or isattached to an intermediate submount member that is subsequentlyattached to the common support member. Candidate materials for thecommon support member or intermediate submount member are SiC, AlN, BeO,diamond, copper, copper tungsten, sapphire, aluminum, or others. Theinterface joining the phosphor to the submount member or common supportmember must be carefully considered. The joining material should becomprised of a high thermal conductivity material such as solder (orother) and be substantially free from voids or other defects that canimpede heat flow. In some embodiments, glue materials can be used tofasten the phosphor. Ideally the phosphor bond interface will have asubstantially large area with a flat surface on both the phosphor sideand the support member sides of the interface.

In the present invention, the laser diode output beam must be configuredto be incident on the phosphor material to excite the phosphor. In someembodiments the laser beam may be directly incident on the phosphor andin other embodiments the laser beam may interact with an optic,reflector, or other object to manipulate the beam prior to incidence onthe phosphor. Examples of such optics include, but are not limited toball lenses, aspheric collimator, aspheric lens, fast or slow axiscollimators, dichroic mirrors, turning mirrors, optical isolators, butcould be others.

The apparatus typically has a free space with a non-guided laser beamcharacteristic transmitting the emission of the laser beam from thelaser device to the phosphor material. The laser beam spectral width,wavelength, size, shape, intensity, and polarization are configured toexcite the phosphor material. The beam can be configured by positioningit at the precise distance from the phosphor to exploit the beamdivergence properties of the laser diode and achieve the desired spotsize. In one embodiment, the incident angle from the laser to thephosphor is optimized to achieve a desired beam shape on the phosphor.For example, due to the asymmetry of the laser aperture and thedifferent divergent angles on the fast and slow axis of the beam thespot on the phosphor produced from a laser that is configured normal tothe phosphor would be elliptical in shape, typically with the fast axisdiameter being larger than the slow axis diameter. To compensate this,the laser beam incident angle on the phosphor can be optimized tostretch the beam in the slow axis direction such that the beam is morecircular on phosphor. In other embodiments free space optics such ascollimating lenses can be used to shape the beam prior to incidence onthe phosphor. The beam can be characterized by a polarization purity ofgreater than 50% and less than 100%. As used herein, the term“polarization purity” means greater than 50% of the emittedelectromagnetic radiation is in a substantially similar polarizationstate such as the transverse electric (TE) or transverse magnetic (TM)polarization states, but can have other meanings consistent withordinary meaning.

The white light apparatus also has an electrical input interfaceconfigured to couple electrical input power to the laser diode device togenerate the laser beam and excite the phosphor material. In an example,the laser beam incident on the phosphor has a power of less than 0.1 W,greater than 0.1 W, greater than 0.5 W, greater than 1 W, greater than 5W, greater than 10 W, or greater than 20 W. The white light sourceconfigured to produce greater than 1 lumen, 10 lumens, 100 lumens, 1000lumens, 10,000 lumens, or greater of white light output.

The support member is configured to transport thermal energy from the atleast one laser diode device and the phosphor material to a heat sink.The support member is configured to provide thermal impedance of lessthan 10 degrees Celsius per watt, less than 5 degrees Celsius per watt,or less than 3 degrees Celsius per watt of dissipated powercharacterizing a thermal path from the laser device to a heat sink. Thesupport member is comprised of a thermally conductive material such ascopper with a thermal conductivity of about 400 W/(mK), aluminum with athermal conductivity of about 200 W/(mK), 4H-SiC with a thermalconductivity of about 370 W/(mK), 6H-SiC with a thermal conductivity ofabout 490 W/(mK), AlN with a thermal conductivity of about 230 W/(mK), asynthetic diamond with a thermal conductivity of about >1000 W/(mK),sapphire, or other metals, ceramics, or semiconductors. The supportmember may be formed from a growth process such as SiC, AlN, orsynthetic diamond, and then mechanically shaped by machining, cutting,trimming, or molding. Alternatively the support member may be formedfrom a metal such as copper, copper tungsten, aluminum, or other bymachining, cutting, trimming, or molding.

In a preferred configuration of this CPoS white light source, the commonsupport member comprises the same submount that the gallium and nitrogencontaining laser diode chip is directly bonded to. That is, the laserdiode chip is mounted down or attached to a submount configured from amaterial such as SiC, AlN, or diamond and the phosphor material is alsomounted to this submount, such that the submount is the common supportmember. The phosphor material may have an intermediate materialpositioned between the submount and the phosphor. The intermediatematerial may be comprised of a thermally conductive material such ascopper. The laser diode can be attached to a first surface of thesubmount using conventional die attaching techniques using solders suchas AuSn solder, but can be other techniques such as SAC solder, leadcontaining phosphor, or indium. Similarly, the phosphor material may bebonded to the submount using a soldering technique such as AuSn solder,SAC solder, lead containing phosphor, or with indium, but it can beother techniques. The joint could also be formed from thermallyconductive glues, thermal epoxies such as silver epoxy, thermaladhesives, and other materials. Alternatively the joint could be formedfrom a metal-metal bond such as a Au—Au bond. Optimizing the bond forthe lowest thermal impedance is a key parameter for heat dissipationfrom the phosphor, which is critical to prevent phosphor degradation andthermal quenching of the phosphor material.

In an alternative configuration of this CPoS white light source, thelaser diode is bonded to an intermediate submount configured between thegallium and nitrogen containing laser chip and the common supportmember. In this configuration, the intermediate submount can becomprised of SiC, AlN, diamond, or other, and the laser can be attachedto a first surface of the submount using conventional die attachingtechniques using solders such as AuSn solder, but can be othertechniques such as. The second surface of the submount can be attachedto the common support member using similar techniques, but could beothers. Similarly, the phosphor material may have an intermediatematerial or submount positioned between the common support member andthe phosphor. The intermediate material may be comprised of a thermallyconductive material such as copper. The phosphor material may be bondedusing a soldering technique. In this configuration, the common supportmember should be configured of a thermally conductive material such ascopper. Optimizing the bond for the lowest thermal impedance is a keyparameter for heat dissipation from the phosphor, which is critical toprevent phosphor degradation and thermal quenching of the phosphormaterial.

In a specific embodiment of the present invention, the CPoS white lightsource is configured for a side-pumped phosphor operated in transmissivemode. In this configuration, the phosphor is positioned in front of thelaser facet that outputs the laser beam such that upon activation thegenerated laser beam is incident on a backside of the phosphor, whereinboth the laser and the phosphor are configured on a support member. Thegallium and nitrogen containing laser diode is configured with a cavitythat has a length greater than 100 um, greater than 500 um, greater than1000 um, or greater than 1500 um long and a width greater than 1 um,greater than 10 um, greater than 20 um, greater than 30 um, or greaterthan 45 um. The cavity is configured with a front facet or mirror andback facet or mirror on the end, wherein the front facet comprises theoutput facet and configured to emit the laser beam incident on thephosphor. The front facet can be configured with an anti-reflectivecoating to decrease the reflectivity or no coating at all therebyallowing radiation to pass through the mirror without excessivereflectivity. In some cases the coating may be configured to slightlyincrease the reflectivity. Since no laser beam is to be emitted from theback end of the cavity member, the back facet or mirror is configured toreflect the radiation back into the cavity. For example, the back facetincludes highly reflective coating with a reflectivity greater than 85%or 95%. In one example, the phosphor is comprised of a ceramic yttriumaluminum garnet (YAG) doped with Ce3+ ions and emits yellow emission.The phosphor is shaped as a block, plate, sphere, cylinder, or othergeometrical form. Specifically, the phosphor geometry primary dimensionsmay be less than 50 um, less than 100 um, less than 200 um, less than500 um, less than 1 mm, or less than 10 mm. Operated in transmissivemode, the phosphor has a first primary side (back side) for receivingthe incident laser beam and at least a second primary side (front side)where most of the useful white light will exit the phosphor to becoupled to the application. The phosphor is attached to the commonsupport member or submount positioned in front of the laser diode outputfacet such that the first primary side of the phosphor configured forreceiving the excitation light will be in the optical pathway of thelaser output beam. The laser beam geometrical shape, size, spectralwidth, wavelength, intensity, and polarization are configured to excitethe phosphor material. An advantage to transmissive mode phosphoroperation is mitigation of the excitation source blocking or impedingany useful white light emitted from the primary emitting surface.Additionally, by exciting from the backside of the phosphor there willnot be an obstruction relating to the excitation source or beam that maymake integration of optics to collimate or project the white lightdifficult. In alternative embodiments the YAG:CE can be configured toemit a green emission. In yet alternative or the same embodiments theYAG can be doped with Eu to emit a red emission. In alternativeembodiments, silicon nitrides or aluminum-oxi-nitrides can be used asthe crystal host materials for red, green, yellow, or blue emissions.

FIG. 11 presents a schematic diagram illustrating a transmissiveembodiment of a CPoS integrated white light source based on aconventional laser diode formed on gallium and nitrogen containingsubstrate technology according to this present invention. The laserbased CPoS white light device is comprised of submount material 301 thatserves as the common support member configured to act as an intermediatematerial between a laser diode chip 302 and a final mounting surface andas an intermediate material between the phosphor material 306 and afinal mounting surface. The submount is configured with electrodes 303and 304 that may be formed with deposited metal layers such as Au. Inone example, Ti/Pt/Au is used for the electrodes. Wirebonds 305 areconfigured to couple the electrical power from the electrodes 303 and304 on the submount to the laser diode chip to generate a laser beamoutput from the laser diode. The laser beam output excites a phosphorplate 306 positioned in front of the output laser facet. The phosphorplate is attached to the submount on a ledge 307 or recessed region. Theelectrodes 303 and 304 are configured for an electrical connection to anexternal power source such as a laser driver, a current source, or avoltage source. Wirebonds can be formed on the electrodes to couple thepower to the laser diode device. Of course this is merely an example ofa configuration and there could be many variants on this embodimentincluding but not limited to different shape phosphors, differentgeometrical designs of the submount or common support member, differentorientations of the laser output beam with respect to the phosphor,different electrode and electrical designs, and others.

FIG. 12 presents a schematic diagram illustrating an alternativetransmissive embodiment of a CPoS integrated white light source basedaccording to the present invention. In this embodiment the gallium andnitrogen containing lift-off and transfer technique is deployed tofabricate a very small and compact submount member with the laser diodechip formed from transferred epitaxy layers. The laser based CPoS whitelight device is comprised of submount material 301 that serves as thecommon support member configured to act as an intermediate materialbetween a laser diode 302 formed in transferred gallium and nitrogencontaining epitaxial layers and a final mounting surface and as anintermediate material between the phosphor plate material 305 and afinal mounting surface. The laser diode or CoS submount is configuredwith electrodes 303 and 304 that may be formed with deposited metallayers and combination of metal layers including, but not limited to Au,Pd, Pt, Ni, Al, titanium, or others. The laser beam output excites aphosphor plate 305 positioned in front of the output laser facet. Thephosphor plate is attached to the submount on a ledge 306 or recessedregion. The electrodes 303 and 304 are configured for an electricalconnection to an external power source such as a laser driver, a currentsource, or a voltage source. Wirebonds can be formed on the electrodesto couple electrical power to the laser diode device to generate a laserbeam output from the laser diode. Of course this is merely an example ofa configuration and there could be many variants on this embodimentincluding but not limited to different shape phosphors, differentgeometrical designs of the submount or common support member, differentorientations of the laser output beam with respect to the phosphor,different electrode and electrical designs, and others.

In many embodiments of the present invention the attachment interfacebetween the phosphor and the common support member must be designed andprocessed with care. The thermal impedance of this attachment jointshould be minimized using a suitable attaching material, interfacegeometry, and attachment process practices for a thermal impedancesufficiently low to allow the heat dissipation. Moreover, the attachmentinterface may be designed for an increased reflectivity to maximize theuseful white light exiting the emission surface of the phosphor.Examples include AuSn solders, SAC solders, lead containing solders,indium solders, indium, and other solders. The joint could also beformed from thermally conductive glues, thermal epoxies, and othermaterials. The common support member with the laser and phosphormaterial is configured to provide thermal impedance of less than 10degrees Celsius per watt or less than 5 degrees Celsius per watt ofdissipated power characterizing a thermal path from the laser device toa heat sink. The support member is comprised of a thermally conductivematerial such as copper, aluminum, SiC, sapphire, AlN, or other metals,ceramics, or semiconductors. The side-pumped transmissive apparatus hasa form factor characterized by a length, a width, and a height. In anexample, the height is characterized by a dimension of less than 25 mmand greater than 0.5 mm, although there may be variations.

To improve the efficiency of the integrated white light source, measurescan be taken to minimize the amount of light exiting from the firstsurface wherein the laser excitation light is incident on the phosphorand maximize the light exiting the second primary white light emissionside of the phosphor where the useful white light exits. Such measurescan include the use of filters, spectrally selective reflectors,conventional mirrors, spatial mirrors, polarization based filters,holographic elements, or coating layers, but can be others.

In one example for a transmissive mode phosphor, a filter is positionedon the backside of the phosphor to reflect the backward propagatingyellow emission toward the front of the phosphor where it has anotheropportunity to exit the primary emitting surface into useful whitelight. In this configuration the reflector would have to be designed tonot block the blue excitation light from the laser. The reflector couldbe configured from the spectrally selective distributed Bragg reflector(DBR) mirror comprised of 2 or more alternating layers with differentrefractive indices designed to reflect yellow light over a wide range ofangles. The DBR could be deposited directly on the phosphor usingtechniques such as e-beam deposition, sputter deposition, or thermalevaporation. Alternatively, the DBR could be in the form of a plate-likeelement that is applied to the phosphor. Since in a typical white lightsource configured from a mixing of yellow and blue emission the yellowemission comprised about 70% of the energy, this approach of reflectingthe yellow light may be a sufficient measure in many applications. Ofcourse, there can be additional variations, modifications, andalternatives.

In another example for a transmissive mode phosphor, a filter system ispositioned on the backside of the phosphor to reflect the backwardpropagating yellow emission and the scattered blue excitation light backtoward the front of the phosphor where it has another opportunity toexit the primary emitting surface into useful white light. The challengeof this configuration is to allow the forward propagating blue pumpexcitation light to pass through the filter without allowing thescattered backward propagating blue light to pass. One approach toovercoming this challenge is deploying a filter designed for incidentangular reflectivity dependence and configuring the laser at an incidentangle wherein the reflectivity is a minimum such as a normal incidence.Again, in this configuration the reflector could be configured from DBRmirrors such that one DBR mirror pair would reflect yellow and a secondDBR pair would serve to reflect the blue light with the determinedangular dependence. The DBR could be deposited directly on the phosphorusing techniques such as e-beam deposition, sputter deposition, orthermal evaporation. Alternatively, the DBR could be in the form of aplate-like element that is applied to the phosphor. Of course, there canbe additional variations, modifications, and alternatives.

FIG. 13 presents a schematic diagram illustrating an alternativetransmissive embodiment of a CPoS integrated white light sourceaccording to the present invention. In this embodiment the gallium andnitrogen containing lift-off and transfer technique is deployed tofabricate a very small and compact submount member with the laser diodechip formed from transferred epitaxy layers. Of course, a conventionalchip on submount embodiment such as that shown in FIG. 4 and in FIG. 11could be used for this embodiment including optical elements forimproved efficiency. The laser based CPoS white light device iscomprised of submount material 301 that serves as the common supportmember configured to act as an intermediate material between a laserdiode 302 formed in transferred gallium and nitrogen containingepitaxial layers and a final mounting surface and as an intermediatematerial between the phosphor plate material 305 and a final mountingsurface. The laser diode or CoS submount is configured with electrodes303 and 304 that may be formed with deposited metal layers andcombination of metal layers including, but not limited to Au, Pd, Pt,Ni, Al, titanium, or others. The laser beam output excites a phosphorplate 305 positioned in front of the output laser facet. In thisembodiment, the phosphor is coated with a material 307 configured toincrease the efficiency of the white source such that more of the usefulwhite light escapes from the primary emitting surface of the phosphor.In this embodiment, the coating 307 is configured to increase thereflectivity of yellow and possibly blue emission to reflect the lightback toward the front emitting surface. The phosphor plate is attachedto the submount on a ledge 306 or recessed region. The electrodes 303and 304 are configured for an electrical connection to an external powersource such as a laser driver, a current source, or a voltage source.Wirebonds can be formed on the electrodes to couple electrical power tothe laser diode device to generate a laser beam output from the laserdiode. Of course this is merely an example of a configuration and therecould be many variants on this embodiment including but not limited todifferent shape phosphors, different geometrical designs of the submountor common support member, different orientations of the laser outputbeam with respect to the phosphor, different electrode and electricaldesigns, and others.

A second approach to overcoming the challenge of reflecting a backwardpropagating blue emission and yellow emission while allowing a forwardblue emission to pass is deploying a filter system that combines ayellow spectrally selective reflector such as a DBR and a polarizationbased reflector for the blue light. Since the blue emission from thelaser excitation source can be highly polarized with polarization ratiosgreater than 90% or greater than 95% and the backward propagatingscattered blue light will have a mixed polarization, the polarizationbased reflector can be configured to allow the polarization state of thelaser diode output beam (eg TE) to freely pass the filter while actingas a reflector to other polarization states. This configuration wouldlikely require two elements that may be combined into a single thingfilm. A first element would be a yellow reflector such as a DBR mirrorpair or another single layer or multi-layer film designed to reflectyellow. The second element would be a polarization sensitive materialsuch as a plastic, ceramic, metal, or glass. The DBR or other yellowreflective material could be deposited directly on the phosphor or onthe polarization filter element using techniques such as e-beamdeposition, sputter deposition, or thermal evaporation. Alternatively,the DBR could be in the form of a plate-like element that is applied tothe phosphor. The polarization sensitive element could be deposited onthe phosphor or positioned, glued, or attached on the backside of thephosphor. Of course, there can be additional variations, modifications,and alternatives.

A third approach to overcoming the challenge of reflecting a backwardpropagating blue emission and yellow emission while allowing a forwardblue emission to pass is deploying a filter system that combines ayellow spectrally selective reflector such as a DBR and a spatial basedreflector for the blue light. This configuration would likely requiretwo elements that may be combined into a single thing film. A firstelement would be a yellow reflector such as a DBR mirror pair or anothersingle layer or multi-layer film designed to reflect yellow. The secondelement would be a comprised of an element to reflect blue and would beapplied to the back of the phosphor in a selective manner such that itwas not present where the laser beam is incident on the phosphor, but ispresent over the area where the laser beam is not incident. The secondelement could be another DBR coating stack or a broadband reflectormaterial such as Ag or Al. Both the first element such as a DBR or otheryellow reflective material and the second element spatially reflectiveto blue light could be deposited directly on the phosphor or on thepolarization filter element using techniques such as e-beam deposition,sputter deposition, or thermal evaporation. Alternatively, the DBR couldbe in the form of a plate-like element that is applied to the phosphor.The polarization sensitive element could be deposited on the phosphor orpositioned, glued, or attached on the backside of the phosphor. Ofcourse, there can be additional variations, modifications, andalternatives.

In other embodiments, coatings or other materials may be used to reducethe reflectivity of the front emission surface of the phosphor. In yetother embodiment, coatings or additional elements may be applied toreduce the reflectivity of the incident beam on the phosphor surface. Inconfigurations where off axis laser beam incident angles are used suchmeasure to reduce the reflectivity of the laser beam on the phosphor maybe critical.

In the present invention, the laser diode output beam must be configuredto be incident on the phosphor material to excite the phosphor. Theapparatus typically has a free space with a non-guided laser beamcharacteristic transmitting the emission of the laser beam from thelaser device to the phosphor material. The laser beam spectral width,wavelength, size, shape, intensity, and polarization are configured toexcite the phosphor material. Specifically, in many applications it isdesirable to have a round laser excitation beam such that theilluminated spot on the phosphor is also round and the resulting whitelight emission radiates from a round area. Such a round area isadvantageous for forming collimated or spot light sources usingconventional optics and reflectors commonly available for roundemission. Additionally, the round beam produces some symmetry in thephosphor so that there are not thermal hotspots which can lead tochanges in phosphor conversion efficiency or even initiate failuremechanisms in the phosphor.

This same concept can also be utilized to generate other shapes such aselliptical, conical, rectangular and others for applications whichrequire non-circular beams. In automotive headlights for example,customized spatial patterns are desired to produce illumination indesired areas, and darker spots in the beam pattern in order to avoidcausing glare to other oncoming drivers.

The inherent divergence properties of the output beams from typicaledge-emitting diode lasers leads to the beam expanding in both thex-direction (slow divergence axis) and y-direction (fast divergenceaxis) as it propagates in free/unguided space. Complicating matters isthe different divergence rates of the beam on the fast and slow axisresulting from the waveguide confinement characteristics in the laserdiode. For example, typical full width at half maximum (FWHM) beamdivergences range from about 5-20 degrees in the slow axis and 10 to 40degrees in the fast axis, but can be others. Another measure ofdivergence of the laser beam is the divergence angles taken at the pointin the output beam where the power has dropped to the 1/e2 level. Forthis 1/e2 measure, typical beam divergences range from about 10-30degrees in the slow axis and 20 to 80 degrees in the fast axis, but canbe others. Thus, the ratio of the fast axis to slow axis divergenceangles range from about 2:1 to about 4:1. The resulting projected spotfrom a free-space/unguided laser beam is an elliptical shape, typicallywith the fast axis diameter being greater than the slow axis diameter.FIG. 14 presents a schematic diagram illustrating a an example of anelliptical output beam from a laser diode with a fast axis divergenceangle of θ₁, a fast axis spot diameter of D₁, a slow axis divergenceangle θ₂, and a slow axis spot diameter of D₂.

FIG. 15 schematically illustrates a simplified example of the geometrythat can be used to compute the beam diameter in the fast or slow axiswith a laser diode a distance L away from a flat surface. To compute thequantitative values of the spot diameters, D1 and D2, the laser diodeaperture dimensions must be known as well as the distance of the flatprojection surface from the laser aperture. FIG. 16 presents a plot ofthe fast axis spot diameter, D1, the slow axis spot diameter, D2, andthe ratio of the fast to slow spot diameters for a varied distance Lfrom the laser aperture. The example calculation of FIG. 16 assumes a1/e2 fast axis divergence of 40 degrees, a 1/e2 slow axis divergence of20 degrees, an aperture width of 25 um, and an aperture height of 1 um.As seen in the figure for this example, for projection surfaces [ie thephosphor] greater than 100 um away from the laser aperture the beamquickly becomes elliptical with the fast axis diameter saturating atabout 2 times greater than the slow axis diameter. At a distance ofabout 70 um away from the aperture, the fast and slow axis diameters arenearly equivalent at about 50 um. Thus, to achieve a most circular spotwith this laser diode configuration, the phosphor should be placed about70 um in front of the laser diode where the spot would be 50 um indiameter. Although it would be advantageous to have a circular beamwithout the use of additional optics for collimation and shaping, such adesign may not be the most practical to implement due to the vicinity ofthe phosphor to the laser which may create assembly and fabricationchallenges. Moreover, the very small beam diameter with very high powersof greater than 1 W or greater than 4 W could cause issues in thephosphor if the phosphor quality and/or heat sinking cannot stand thehigh power density. However, when moving the phosphor further from theaperture, the beam quickly becomes elliptical which in many applicationswould not be as ideal as a round spot.

In one embodiment of the present invention a collimating optic ispositioned between the laser diode and the phosphor to collimate andbeam shape the laser output beam. By placing a free space optic in frontof the output laser beam the beam shape can be shaped to provide acircular beam profile and collimated such that the phosphor can bepositioned at a distance in front of the facet with a large toleranceand maintain a relatively constant spot size. In one example an asphericlens is used to collimate and/or shape the laser beam. In an alternativeembodiment, the laser beam is collimated using fast axis collimating(FAC) and/or slow axis collimating (SAC) lenses. In alternativeembodiments, other optics can be included in various combinations forthe shaping, collimating, directing, filtering, or manipulating of theoptical beam. Examples of such optics include, but are not limited toball lenses, aspheric collimator, dichroic mirrors, turning mirrors,optical isolators, but could be others.

FIG. 17 presents a schematic diagram illustrating a transmissivephosphor embodiment of a CPoS integrated white light source includingfree-space optics to collimate and shape the laser beam for incidence onthe phosphor according to the present invention. In this embodiment thegallium and nitrogen containing lift-off and transfer technique isdeployed to fabricate a very small and compact submount member with thelaser diode chip formed from transferred epitaxy layers. Of course, aconventional chip on submount embodiment such as that shown in FIG. 4and in FIG. 11 could be used for this integrated free-space opticembodiment. The laser based CPoS white light device is comprised ofsubmount material 301 that serves as the common support memberconfigured to act as an intermediate material between a laser diode 302formed in transferred gallium and nitrogen containing epitaxial layersand a final mounting surface and as an intermediate material between thephosphor plate material 305 and a final mounting surface. The laserdiode and/or submount is configured with electrodes 303 and 304 that maybe formed with deposited metal layers and combination of metal layersincluding, but not limited to Au, Pd, Pt, Ni, Al, titanium, or others.The laser beam output is coupled into an aspheric lens 305 forcollimation and beam shaping to create a more circular beam, which thenexcites a phosphor plate 305 positioned in front of aspheric lens. Thephosphor plate is attached to the submount on a ledge 307 or recessedregion. The electrodes 303 and 304 are configured for an electricalconnection to an external power source such as a laser driver, a currentsource, or a voltage source. Wirebonds can be formed on the electrodesto couple electrical power to the laser diode device to generate a laserbeam output from the laser diode. Of course this is merely an example ofa configuration and there could be many variants on this embodimentincluding but not limited to different shape phosphors, differentgeometrical designs of the submount or common support member, differentorientations of the laser output beam with respect to the phosphor,different electrode and electrical designs, and others.

In an alternative preferred embodiment, beam shaping can achieved bytilting the phosphor excitation surface with respect the laser diodeaperture and positioning the laser diode at a designed distance from thephosphor to exploit the beam divergence properties of the laser diodeand achieve the desired spot size. This “optics-less” beam shapingembodiment is advantageous over embodiments where optical elements areintroduced for beam shaping and collimation. These advantages of thisembodiment for the white light source apparatus include a simplifieddesign, a lower cost bill of materials, a lower cost assembly process,and potentially a more compact white light source. In one embodiment,the incident angle from the laser to the phosphor is optimized toachieve a desired beam shape on the phosphor. As discussed for theexample of FIG. 16, by positioning the phosphor about 70 um away fromthe laser aperture a relative uniform beam can be realized with about a50 um diameter. In addition to controlling the distance of the laserfrom the phosphor, the incident angle of the laser beam can also be usedto control the shape of the beam incident on the phosphor. As anexample, FIG. 18 shows the effect on the spot size when the phosphor orprojection surface is tilted with respect to the fast axis. By tiltingalong this axis a larger fast axis diameter D1 is generated on thephosphor such that the beam spot becomes more elliptical. By the sameprinciple, as illustrated in FIG. 19, when rotating the phosphor orprojection surface about the slow axis, the slow axis diameter D2 can beincreased such that the spot diameter ratio becomes closer to 1 and thebeam becomes more circular.

FIG. 20 schematically illustrates a simplified example of the geometrythat can be used to compute the beam diameter (r1+r2) in the fast orslow axis with a laser diode a distance L away from a tilted phosphor orprojection surface that is tilted at an angle ω from the fast or slowaxis. By performing the geometry and optimization sequence and optimalphosphor tilt angle can be determined for a relatively circular beamshape. For example, FIG. 21 presents a plot of the fast axis spotdiameter, D1, the slow axis spot diameter, D2, and the ratio of the fastto slow spot diameters for a varied distance L from the laser apertureassuming a phosphor tilt angle of 33 degrees with respect to the slowaxis. The example calculation of FIG. 21 assumes a 1/e2 fast axisdivergence of 40 degrees, a 1/e2 slow axis divergence of 20 degrees, anaperture width of 25 um, and an aperture height of 1 um. As seen in thefigure for this example, for projection surfaces such as the phosphor abeam ratio of 1 occurs at a distance L of about 600 um separating thelaser aperture and phosphor, wherein beam the diameters, D1 and D2, areabout 500 um. This configuration is optimized for maintaining even abeam ratio of 1 over large ranges of L and corresponding spot size.

FIG. 22 presents a schematic diagram illustrating a transmissivephosphor embodiment of a CPoS integrated white light source including atilted phosphor design to achieve a more circular excitation spot on thelaser according to the present invention. In this embodiment aconventional full laser diode chip containing substrate is mounted onthe submount. The laser based CPoS white light device is comprised ofsubmount material 301 that serves as the common support memberconfigured to act as an intermediate material between a laser diode chip302 and a final mounting surface and as an intermediate material betweenthe phosphor plate material 306 and a final mounting surface. The laserdiode or CoS is configured with electrodes 303 and 304 that may beformed with deposited metal layers and combination of metal layersincluding, but not limited to Au, Pd, Pt, Ni, Al, titanium, or others.Wirebonds 305 are configured to couple the electrical power from theelectrodes 303 and 304. The phosphor plate 306 is tilted about the slowaxis of the laser diode output to result in a more circular excitationspot on the phosphor. For example, the phosphor could be at an angle ofabout 33 degrees according to the calculation in FIG. 20. The phosphorplate is attached to the submount on a ledge 307 or recessed region. Theelectrodes 303 and 304 are configured for an electrical connection to anexternal power source such as a laser driver, a current source, or avoltage source. Wirebonds can be formed on the electrodes to coupleelectrical power to the laser diode device to generate a laser beamoutput from the laser diode. Of course this is merely an example of aconfiguration and there could be many variants on this embodimentincluding but not limited to different shape phosphors, differentphosphor angle or orientation, different geometrical designs of thesubmount or common support member, different orientations of the laseroutput beam with respect to the phosphor, different electrode andelectrical designs, and others.

FIG. 23 presents a schematic diagram illustrating a transmissivephosphor embodiment of a CPoS integrated white light source including atilted phosphor design to achieve a more circular excitation spot on thelaser according to the present invention. In this embodiment the galliumand nitrogen containing lift-off and transfer technique is deployed tofabricate a very small and compact submount member with the laser diodechip formed from transferred epitaxy layers. Of course, a conventionalchip on submount embodiment such as that shown in FIG. 4 and in FIG. 11could be used for this tilted phosphor embodiment. The laser based CPoSwhite light device is comprised of submount material 301 that serves asthe common support member configured to act as an intermediate materialbetween a laser diode 302 formed in transferred gallium and nitrogencontaining epitaxial layers and a final mounting surface and as anintermediate material between the phosphor plate material 305 and afinal mounting surface. The laser diode or CoS is configured withelectrodes 303 and 304 that may be formed with deposited metal layersand combination of metal layers including, but not limited to Au, Pd,Pt, Ni, Al, titanium, or others. The phosphor plate 305 is tilted aboutthe slow axis of the laser diode output to result in a more circularexcitation spot on the phosphor. For example, the phosphor could be atan angle of about 33 degrees according to the calculation in FIG. 20.The phosphor plate is attached to the submount on a ledge 307 orrecessed region. The electrodes 303 and 304 are configured for anelectrical connection to an external power source such as a laserdriver, a current source, or a voltage source. Wirebonds can be formedon the electrodes to couple electrical power to the laser diode deviceto generate a laser beam output from the laser diode. Of course this ismerely an example of a configuration and there could be many variants onthis embodiment including but not limited to different shape phosphors,different phosphor angle or orientation, different geometrical designsof the submount or common support member, different orientations of thelaser output beam with respect to the phosphor, different electrode andelectrical designs, and others.

In alternative embodiments of the present invention, multiple phosphorsare operated in a transmissive mode for a white emission. In oneexample, a violet laser diode configured to emit a wavelength of 395 nmto 425 nm and excite a first blue phosphor and a second yellow phosphor.In this configuration, a first blue phosphor plate could be fused orbonded to the second yellow phosphor plate. In a practical configurationthe laser beam would be directly incident on the first blue phosphorwherein a fraction of the blue emission would excite the second yellowphosphor to emit yellow emission to combine with blue emission andgenerate a white light. Additionally, the violet pump would essentiallyall be absorbed since what may not be absorbed in the blue phosphorwould then be absorbed in the yellow phosphor. In an alternativepractical configuration the laser beam would be directly incident on thesecond yellow phosphor wherein a fraction of the violet electromagneticemission would be absorbed in the yellow phosphor to excite yellowemission and the remaining violet emission would pass to the bluephosphor and create a blue emission to combine a yellow emission with ablue emission and generate a white light.

In an alternative embodiment of a multi-phosphor transmissive exampleaccording to the present invention, a blue laser diode operating with awavelength of 425 nm to 480 nm is configured to excite a first greenphosphor and a second red phosphor. In this configuration, a first greenphosphor plate could be fused or bonded to the second red phosphorplate. In a practical configuration the laser beam would be directlyincident on the first green phosphor wherein a fraction of the greenemission would excite the second red phosphor to emit red emission tocombine with green phosphor emission and blue laser diode emission togenerate a white light. In an alternative practical configuration thelaser beam would be directly incident on the second red phosphor whereina fraction of the blue electromagnetic emission would be absorbed in thered phosphor to excite red emission and a portion of the remaining bluelaser emission would pass to the green phosphor and create a greenemission to combine with the red phosphor emission and blue laser diodeemission to generate a white light. The benefit or feature of thisembodiment is the higher color quality that could be achieved from awhite light comprised of red, green, and blue emission. Of course therecould be other variants of this invention including integrating morethan two phosphor and could include one of or a combination of a red,green, blue, and yellow phosphor.

In yet another variation of a side pumped phosphor configuration, a“point source” or “point source like” CPoS white emitting device isachieved. In this configuration the phosphor would have a 3-dimensionalgeometry such as a cube geometry or a spherical geometry such that whitelight can be emitted from multiple primary emission surfaces, andideally from the entirety of the surface area of the 3-dimensionalphosphor geometry. For example, in a cube geometry up to all six facesof the cube can emit white light or in a sphere configuration the entiresurface can emit to create a perfect point source. In some practicalimplementations of this present invention, certain surfaces of the3-dimension phosphor geometry may not be to freely emit due toobstructions or impediments. For example, in some configurations of thisembodiment the phosphor is attached to the common support member whereinthe common support member may not be fully transparent. In thisconfiguration the mounting surface or support member would be impede thephosphor emission from the side or portion of the phosphor facing themounting surface or support member. This impediment would reduce theoverall efficiency or quality of the point source white light emitter.However, this emission impediment can be minimized or mitigated usingvarious techniques to provide a very efficient point source. In oneconfiguration, the phosphor is supported by an optically transparentmember such that the light is free to emit in all directions from thephosphor point source. In one variation, the phosphor is fullysurrounded in or encapsulated by an optically transparent material suchas a solid material like SiC, sapphire, diamond, GaN, or other, or aliquid material like water or a more thermally conductive liquid.

FIG. 24 presents a schematic diagram illustrating a point sourcelaser-pumped phosphor embodiment of a CPoS integrated white light sourceincluding a phosphor with a 3-dimensional geometrical design to providea point source of light according to the present invention. In thisembodiment the gallium and nitrogen containing lift-off and transfertechnique is deployed to fabricate a very small and compact submountmember with the laser diode chip formed from transferred epitaxy layers.Of course, a conventional chip on submount embodiment such as that shownin FIG. 4 and in FIG. 11 could be used for this point source embodiment.The laser based CPoS white light device is comprised of submountmaterial 301 that serves as the common support member configured to actas an intermediate material between a laser diode 302 formed intransferred gallium and nitrogen containing epitaxial layers and a finalmounting surface and as an intermediate material between the phosphorplate material 305 and a final mounting surface. The laser diode or CoSis configured with electrodes 303 and 304 that may be formed withdeposited metal layers and combination of metal layers including, butnot limited to Au, Pd, Pt, Ni, Al, titanium, or others. The3-dimensional phosphor member 305 is configured in front of the laserdiode such that the output laser beam 306 is incident on an excitationside of the phosphor and multiple sides of the phosphor are configuredto emit white light. Up to all sides of the phosphor can emit, but insome embodiments such as that shown in FIG. 24 the emission may beobstructed from the mounting surface where the phosphor is attached tothe submount on a ledge 307 or recessed region. The electrodes 303 and304 are configured for an electrical connection to an external powersource such as a laser driver, a current source, or a voltage source.Wirebonds can be formed on the electrodes to couple electrical power tothe laser diode device to generate a laser beam 306 output from thelaser diode. Of course this is merely an example of a configuration andthere could be many variants on this embodiment including but notlimited to different shape phosphors such as spherical or semispherical,different phosphor angle or orientation, different geometrical designsof the submount or common support member, different orientations of thelaser output beam with respect to the phosphor, different electrode andelectrical designs, and others.

In other variations, the support member can be used to manipulate thelight in the integrated white light source. In one example, an opticallytransparent support member could serve as a waveguide for the laserlight to reach the phosphor. In another example, an opticallytransparent support member can be configured to transmit the laser lightto the phosphor member. In other examples of this variation wherein thesupport member manipulates the light, the support member can be shapedor configured to form reflectors, mirrors, diffusers, lenses, absorbers,or other members to manipulate the light. In another variation, thesupport member could also serve as a protective safety measure to ensurethat no direct emitting laser light is exposed as it travels to reachthe phosphor. Such point sources of light that produce trueomni-directional emission are increasing useful as the point sourcebecomes increasing smaller, due to the fact that product of the emissionaperture and the emission angle is conserved or lost as subsequentoptics and reflectors are added. Specifically, for example, a smallpoint source can be collimated with small optics or reflectors. However,if the same small optics or reflector assembly are applied to a largepoint source, the optical control and collimation is diminished.

In another specific preferred embodiment of the CPoS white light source,the present invention is configured for a reflective mode phosphoroperation. In one example the excitation laser beam enters the phosphorthrough the same primary surface as the useful white light is emittedfrom. That is, operated in reflective mode the phosphor could have afirst primary surface configured for both receiving the incidentexcitation laser beam and emitting useful white light. In thisconfiguration, the phosphor is positioned in front of the laser facetthat outputs the laser beam, wherein both the laser and the phosphor areconfigured on a support member. The gallium and nitrogen containinglaser diode is configured with a cavity that has a length greater than100 um, greater than 500 um, greater than 1000 um, or greater than 1500um long and a width greater than 1 um, greater than 10 um, greater than20 um, greater than 30 um, or greater than 45 um. The cavity isconfigured with a front facets and back facet on the end wherein thefront facet comprises the output facet and emits the laser beam incidenton the phosphor. The front facet can be configured with ananti-reflective coating to decrease the reflectivity or no coating atall thereby allowing radiation to pass through the mirror withoutexcessive reflectivity. In some cases the coating may be configured toslightly increase the reflectivity. Since no laser beam is to be emittedfrom the back end of the cavity member, the back facet or mirror isconfigured to reflect the radiation back into the cavity. For example,the back facet includes highly reflective coating with a reflectivitygreater than 85% or 95%. In one example, the phosphor can be comprisedof Ce doped YAG and emits yellow emission. The phosphor may be a ceramicphosphor and could be a single crystal phosphor. The phosphor ispreferably shaped as a substantially flat member such as a plate or asheet with a shape such as a square, rectangle, polygon, circle, orellipse, and is characterized by a thickness. In a preferred embodimentthe length, width, and or diameter dimensions of the large surface areaof the phosphor are larger than the thickness of the phosphor. Forexample, the diameter, length, and/or width dimensions may be 2× greaterthan the thickness, 5× greater than the thickness, 10× greater than thethickness, or 50× greater than the thickness. Specifically, the phosphorplate may be configured as a circle with a diameter of greater than 50um, greater than 100 um, greater than 200 um, greater than 500 um,greater than 1 mm, or greater than 10 mm and a thickness of less than500 um, less than 200 um, less than 100 um or less than 50 um. A keybenefit to a reflective mode phosphor is the ability to configure it forexcellent heat dissipation since the backside of surface of the phosphorcan be directly heat-sunk to the common support member or intermediatesubmount member. Since the phosphor is preferably thin, the thermal pathis short and can rapidly travel to the support member. In alternative orthe same embodiments a YAG:CE can be configured to emit a greenemission. In yet alternative or the same embodiments the YAG can bedoped with Eu to emit a red emission. In alternative embodiments,silicon nitrides or aluminum-oxi-nitrides can be used as the crystalhost materials for red, green, yellow, or blue emissions.

In one example of the reflective mode CPoS white light source embodimentof this invention optical coatings, material selections, or specialdesign considerations are taken to improve the efficiency by maximizingthe amount of light exiting the primary surface of the phosphor. In oneexample, the backside of the phosphor may be coated with reflectivelayers or have reflective materials positioned on the back surface ofthe phosphor adjacent to the primary emission surface. The reflectivelayers, coatings, or materials help to reflect the light that hits theback surface of the phosphor such that the light will bounce and exitthrough the primary surface where the useful light is captured. In oneexample, a coating configured to increase the reflectivity for yellowlight and blue light is applied to the phosphor prior to attaching thephosphor to the common support member. Such coatings could be comprisedof metal layers such as silver or aluminum, or others such as gold,which would offer good thermal conductivity and good reflectance orcould be comprised of dielectric layers configured as single layers,multi layers, or DBR stacks, but could be others. In another example, areflective material is used as a bonding medium that attaches thephosphor to the support member or to an intermediate submount member.Examples of reflective materials include reflective solders like AuSn,SnAgC (SAC), or Pb containing phosphors, or reflective glues, but couldbe others. With respect to attaching the phosphor to the common supportmember, thermal impedance is a key consideration. The thermal impedanceof this attachment joint should be minimized using the best attachingmaterial, interface geometry, and attachment process practices for thelowest thermal impedance with sufficient reflectivity. Examples includeAuSn solders, SAC solders, Pb containing solders, indium, and othersolders. The joint could also be formed from thermally conductive glues,thermal epoxies such as silver epoxy, thermal adhesives, and othermaterials. Alternatively the joint could be formed from a metal-metalbond such as a Au—Au bond. The common support member with the laser andphosphor material is configured to provide thermal impedance of lessthan 10 degrees Celsius per watt or less than 5 degrees Celsius per wattof dissipated power characterizing a thermal path from the laser deviceto a heat sink. The support member is comprised of a thermallyconductive material such as copper, aluminum, SiC, sapphire, AlN, orother metals, ceramics, or semiconductors. The reflective mode whitelight source apparatus has a form factor characterized by a length, awidth, and a height. In an example, the height is characterized by adimension of less than 25 mm and greater than 0.5 mm, although there maybe variations. In an alternative example, the height is characterized bya dimension of less than 12.5 mm, and greater than 0.5 mm, althoughthere may be variations. In yet an alternative example, the length andwidth are characterized by a dimension of less than 30 mm, less than 15mm, or less than 5 mm, although there may be variations.

The reflective mode CPoS white light source embodiment of this inventionis configured with the phosphor member attached to the common supportmember with the large primary surface configured for receiving laserexcitation light and emitting useful white light positioned at an anglenormal (about 90 degrees) or off-normal (about 0 degrees to about 89degrees) to the axis of the laser diode output beam functioning toexcite the phosphor. That is, the laser output beam is pointing towardthe phosphor's emission surface at an angle of between 0 and 90 degrees,wherein 90 degrees (orthogonal) is considered normal incidence. Theinherent geometry of this configuration wherein the laser beam isdirected away from or in an opposite direction that the useful whitelight will exit the phosphor toward the outside world is ideal forsafety. As a result of this geometry, if the phosphor get damaged orremoved during operation or from tampering, the laser beam would not bedirected to the outside world where it could be harmful. Instead, thelaser beam would be incident on the backing surface where the phosphorwas attached. With proper design of this backing surface the laser beamcan be scattered, absorbed, or directed away from the outside worldinstead of exiting the white light source and into the surroundingenvironment.

In one embodiment of this reflective mode CPoS white light source thelaser beam is configured normal to the primary phosphor emissionsurface. In this configuration the laser diode would be positioned infront of the primary emission surface of the phosphor where it couldimpede the useful white light emitted from the phosphor. This couldcreate losses in or inefficiencies of the white light device and wouldlead to difficulty in efficiently capturing all white light emitted fromthe phosphor. Such optics and reflectors include, but are not limited toaspheric lenses or parabolic reflectors. To overcome the challenges ofnormal incident reflective mode phosphor excitation, in a preferableembodiment the laser beam would be configured with an incident anglethat is off-axis to the phosphor such that it hits the phosphor surfaceat an angle of between 0 and 89 degrees or at a “grazing” angle. In thispreferable embodiment the laser diode device is positioned adjacent toor to the side of the phosphor instead of in front of the phosphor whereit will not substantially block or impede the emitted white light, andimportantly, allow for optics such as collimating lenses or reflectorsto access the useful light and project it to the application.Additionally, in this configuration the built in safety feature is moreoptimal than in the normal incidence configuration since when incidentat an angle in the case of phosphor damage or removal the incident laserbeam would not reflect directly off the back surface of the supportmember where the phosphor was attached. By hitting the surface at anoff-angle or a grazing angle any potential reflected components of thebeam can be directed to stay within the apparatus and not exit theoutside environment where it can be a hazard to human beings, animals,and the environment.

FIG. 25 presents a schematic diagram illustrating an off-axis reflectivemode embodiment of a CPoS integrated white light source according to thepresent invention. In this embodiment the gallium and nitrogencontaining lift-off and transfer technique is deployed to fabricate avery small and compact submount member with the laser diode chip formedfrom transferred epitaxy layers. Further, in this example the phosphoris tilted with respect to the fast axis of the laser beam at an angleω₁. The laser based CPoS white light device is comprised of a commonsupport member 401 that serves as the common support member configuredto act as an intermediate material between a laser diode or laser diodeCoS 402 formed in transferred gallium and nitrogen containing epitaxiallayers 403 and a final mounting surface and as an intermediate materialbetween the phosphor plate material 406 and a final mounting surface.The laser diode or CoS is configured with electrodes 404 and 405 thatmay be formed with deposited metal layers and combination of metallayers including, but not limited to Au, Pd, Pt, Ni, Al, titanium, orothers. The laser beam output excites a phosphor plate 406 positioned infront of the output laser facet. The phosphor plate is attached to thecommon support member on a surface 408. The electrodes 404 and 405 areconfigured for an electrical connection to an external power source suchas a laser driver, a current source, or a voltage source. Wirebonds canbe formed on the electrodes to couple electrical power to the laserdiode device to generate a laser beam 407 output from the laser diodeand incident on the phosphor 406. Of course this is merely an example ofa configuration and there could be many variants on this embodimentincluding but not limited to different shape phosphors, differentgeometrical designs of the submount or common support member, differentorientations of the laser output beam with respect to the phosphor,different electrode and electrical designs, and others.

The inherent divergence properties typical edge-emitting diode laseroutput beams leads to the beam expanding in both the x-direction (slowdivergence axis) and y-direction (fast divergence axis) as it propagatesin free/unguided space. Complicating matters is the different divergencerates of the beam on the fast and slow axis resulting from the waveguideconfinement characteristics in the laser diode. For example, typicalfull width at half maximum (FWHM) beam divergences range from about 5-20degrees in the slow axis and 10 to 40 degrees in the fast axis, but canbe others. Another measure of divergence of the laser beam is thedivergence angles taken at the point in the output beam where the powerhas dropped to the 1/e2 level. For this 1/e2 measure, typical beamdivergences range from about 10-30 degrees in the slow axis and 20 to 80degrees in the fast axis, but can be others. Thus, the ratio of the fastaxis to slow axis divergence angles range from about 2:1 to about 4:1.The resulting projected spot from a free-space/unguided laser beam is anelliptical shape, typically with the fast axis diameter being greaterthan the slow axis diameter. For a laser beam configured for off-axisincidence in the fast direction as shown in FIG. 25 the ellipticalnature of the beam would be exacerbated since the angle would increasethe fast axis diameter D1 as shown in FIG. 18.

In one embodiment of the present invention, the elliptical nature of thebeam from the beam divergence and off-axis laser beam excitationincidence would be mitigating using a beam shaping optic such as acollimating optic. This optic would be positioned between the laserdiode and the phosphor to shape and/or collimate the laser output beamprior to incidence with the phosphor. By placing a free space optic infront of the output laser beam the beam shape can be shaped to provide acircular beam profile and collimated such that the phosphor can bepositioned at a distance in front of the facet with a large toleranceand maintain a relatively constant spot size. In one example an asphericlens is used to collimate and/or shape the laser beam. In an alternativeembodiment, the laser beam is collimated using fast axis collimating(FAC) and/or slow axis collimating (SAC) lenses. In alternativeembodiments, other optics can be included in various combinations forthe shaping, collimating, directing, filtering, or manipulating of theoptical beam. Examples of such optics include, but are not limited toball lenses, aspheric collimator, dichroic mirrors, turning mirrors,optical isolators, but could be others.

FIG. 26 presents a schematic diagram illustrating an off-axis reflectivemode embodiment of a CPoS integrated white light source according to thepresent invention. In this embodiment the gallium and nitrogencontaining lift-off and transfer technique is deployed to fabricate avery small and compact submount member with the laser diode chip formedfrom transferred epitaxy layers. Further, in this example the phosphoris tilted with respect to the fast axis of the laser beam at an angleω₁. The laser based CPoS white light device is comprised of a commonsupport member 401 that serves as the common support member configuredto act as an intermediate material between a laser diode or laser diodeCoS 402 formed in transferred gallium and nitrogen containing epitaxiallayers 403 and a final mounting surface and as an intermediate materialbetween the phosphor plate material 406 and a final mounting surface.The laser diode or CoS is configured with electrodes 404 and 405 thatmay be formed with deposited metal layers and combination of metallayers including, but not limited to Au, Pd, Pt, Ni, Al, titanium, orothers. The laser beam is passed through an aspheric lens 407 for beamshaping and/or collimating prior to incidence on a phosphor plate 406.The phosphor plate is attached to the common support member on a surface408. The electrodes 404 and 405 are configured for an electricalconnection to an external power source such as a laser driver, a currentsource, or a voltage source. Wirebonds can be formed on the electrodesto couple electrical power to the laser diode device to generate a laserbeam 407 output from the laser diode and incident on the phosphor 406.Of course this is merely an example of a configuration and there couldbe many variants on this embodiment including but not limited todifferent shape phosphors, different geometrical designs of the submountor common support member, different orientations of the laser outputbeam with respect to the phosphor, different electrode and electricaldesigns, and others.

In an alternative preferred off-axis reflective mode embodiment, beamshaping can be achieved by rotating the laser beam with respect to thetilted phosphor excitation surface. By rotating the laser about the axisof the beam emission, the phosphor tilt will shift from increasing thefast axis beam diameter to the increasing the slow axis beam diameter,and hence, compensate for the slower diverging slow axis beam axisdiameter and make for a more circular beam. This dual-axis tilting orrotation embodiment of “optics-less” beam shaping is advantageous overembodiments where optical elements are introduced for beam shaping andcollimation. The advantages of this embodiment for the white lightsource apparatus include a simplified design, a lower cost bill ofmaterials, a lower cost assembly process, and potentially a more compactwhite light source. In one embodiment, the incident angle from the laserto the phosphor is optimized to achieve a desired beam shape on thephosphor.

As discussed for the example of FIG. 16, by positioning the phosphorabout 70 um away from the laser aperture a relative uniform beam can berealized with about a 50 um diameter. In addition to controlling thedistance of the laser from the phosphor, the incident angle of the laserbeam can also be used to control the shape of the beam incident on thephosphor. As an example, FIG. 18 shows the effect on the spot size whenthe phosphor or projection surface is tilted with respect to the fastaxis. By tilting along this axis a larger fast axis diameter D1 isgenerated on the phosphor such that the beam spot becomes moreelliptical. By the same principle, as illustrated in FIG. 19, whenrotating the phosphor or projection surface about the slow axis, theslow axis diameter D2 can be increased such that the spot diameter ratiobecomes closer to 1 and the beam becomes more circular.

For a given phosphor tilt (ω₁) with respect to the fast axis, therotation of the laser beam spot (ω₂) can be optimized to realize a morecircular beam shape on the phosphor. As an example, FIG. 27 presents aplot of the fast axis spot diameter, D1, the slow axis spot diameter,D2, and the ratio of the fast to slow spot diameters for a varieddistance L from the laser aperture assuming a phosphor tilt angle (ω₁)of 45 degrees with respect to the fast axis and a laser rotation (ω₂) of22 degrees to tilt the beam with respect to the slow axis. The examplecalculation of FIG. 27 assumes a 1/e2 fast axis divergence of 40degrees, a 1/e2 slow axis divergence of 20 degrees, an aperture width of25 um, and an aperture height of 1 um. As seen in the figure for thisexample, for projection surfaces such as the phosphor the beam ratiorapidly approaches 1 at a distance L of about 200 um and saturates to 1at a distance L of about 800 um. Thus, in this example, a beam with adiameter ratio of about 1 can be achieve for a distance L of 200 um andgreater where a desired spot size with a diameter of 200 um and greatercan be achieved.

FIG. 28 presents a schematic diagram illustrating an off-axis reflectivemode embodiment of a CPoS integrated white light source with a laserrotation according to the present invention. In this embodiment thegallium and nitrogen containing lift-off and transfer technique isdeployed to fabricate a very small and compact submount member with thelaser diode chip formed from transferred epitaxy layers. In this examplethe phosphor is tilted with respect to the fast axis of the laser beamat an angle ω1 and the laser is rotated at an angle ω1 with respect tothe slow axis. The laser based CPoS white light device is comprised of acommon support member 401 that serves as the common support memberconfigured to act as an intermediate material between a laser diode orlaser diode CoS 402 formed in transferred gallium and nitrogencontaining epitaxial layers 403 and a final mounting surface and as anintermediate material between the phosphor plate material 406 and afinal mounting surface. The laser diode or CoS is configured withelectrodes 404 and 405 that may be formed with deposited metal layersand combination of metal layers including, but not limited to Au, Pd,Pt, Ni, Al, titanium, or others. The laser beam output excites aphosphor plate 406 positioned in front of the output laser facet. Thephosphor plate is attached to the common support member on a surface408. The electrodes 404 and 405 are configured for an electricalconnection to an external power source such as a laser driver, a currentsource, or a voltage source. Wirebonds can be formed on the electrodesto couple electrical power to the laser diode device to generate a laserbeam 407 output from the laser diode and incident on the phosphor 406.Of course this is merely an example of a configuration and there couldbe many variants on this embodiment including but not limited todifferent shape phosphors, different geometrical designs of the submountor common support member, different orientations of the laser outputbeam with respect to the phosphor, different electrode and electricaldesigns, and others.

Of course the reflective mode embodiment configurations shown in FIG.25, FIG. 26, and FIG. 28 are merely just examples and there are a widerange of other arrangements, geometries, and designs. In a specificexample, in an alternative embodiment of this dual rotation off-axislaser beam incident configuration the phosphor can be tilted withrespect to the slow axis of the laser diode instead of rotating thelaser diode as shown in FIG. 28. One benefit to this alternativeembodiment would be a simplification of the common support membergeometry, which may be easier to manufacture. However, the drawback tothis alternative embodiment is that the phosphor would no longerparallel to the horizontal base, which could create difficulties incollecting and collimating the useful white light. In the examples forFIGS. 25, 26, and 28 the phosphor was held at a horizontal orientationand the laser was rotated/tilted to achieve the desired laser incidenceconfiguration. However, this is just an example and in otherarrangements the phosphor may be tilted with respect to the horizontalaxis.

A consideration for the example in FIG. 28 of the present inventionwhere in the laser diode is rotated about its emission axis is thepolarization of the emitted laser beam. Because the phosphor and laserare co-packaged together, the need for an environmentally protectivewindow on the phosphor is eliminated. This results in a high efficiencyfeature of the design because reflection losses of a window areeliminated. Specifically, by utilizing a highly polarized laser diodewith the polarization as stated, substantial losses (ie >30%) areeliminated since this is s-polarized incident light onto the phosphor.By co-packaging, we avoid this window and avoid the >30% losses. Indesigns where the laser and phosphor are not co-packaged, a window onthe phosphor is needed, and the laser light coming onto the window wouldexperience substantial reflection of roughly 30% or more. It may bepossible to apply anti-reflective coatings on this window, but it wouldneed to be an expensive and complex reflective coating design since thelaser light is incoming on the window with a variety of emission anglessince the laser light may not be collimated.

In other variations, the support member can be used to manipulate thelight in the integrated white light source. In one example, an opticallytransparent support member could serve as a waveguide for the laserlight to reach the phosphor. In another example, an opticallytransparent support member can be configured to transmit the laser lightto the phosphor member. In other examples of this variation wherein thesupport member manipulates the light, the support member can be shapedor configured to form reflectors, mirrors, diffusers, lenses, absorbers,or other members to manipulate the light. In another variation, thesupport member could also serve as a protective safety measure to ensurethat no direct emitting laser light is exposed as it travels to reachthe phosphor. Such point sources of light that produce trueomni-directional emission are increasing useful as the point sourcebecomes increasing smaller, due to the fact that product of the emissionaperture and the emission angle is conserved or lost as subsequentoptics and reflectors are added. Specifically, for example, a smallpoint source can be collimated with small optics or reflectors. However,if the same small optics or reflector assembly are applied to a largepoint source, the optical control and collimation is diminished.

In all embodiments of the CPoS white light source final packaging wouldneed to be considered. There are many aspects of the package that shouldbe accounted for such as form factor, cost, functionality, thermalimpedance, sealing characteristics, and basic compatibility with theapplication. Form factor will depend on the application, but in generalmaking the smallest size packaged white source will be desirable. Costshould be minimized in all applications, but in some applications costwill be the most important consideration. In such cases using anoff-the-shelf packages produced in high volume may be desirable.Functionality options include direction and properties of the exitinglight emission for the application as well as integration of featuressuch as photodectors, thermistors, or other electronics oroptoelectronics. For best performance and lifetime the thermal impedanceof the package should be minimized, especially in high powerapplications.

The package is characterized by a sealing configuration. One example ofa sealing configuration includes open environment wherein the whitelight source is subjected to the ambient conditions. In some embodimentwith robust laser diode and phosphor designs intended for openenvironment operation this embodiment is favorable. As an example, thelaser diode chip may be encapsulated in a protective layer to preventoxidation, chemical reaction, or contamination of the laser diode. Insome embodiments the laser is formed from a substantially aluminum freenonpolar or semipolar design wherein the laser diode facet regions areless prone to oxidation and degradation. Similarly, the phosphor canalso be encapsulated in a protective layer to prevent oxidation,chemical reaction, or contamination of the phosphor.

In preferred embodiments of the present invention, the integrated whitelight source is characterized with an environmentally sealed package ora hermetically sealed package. For an environmentally sealedconfiguration, the package enclosure prevents dust and other particlesfrom interacting with the laser or phosphor. For hermetically sealedpackages, the package should be leak tight and characterized by a verysmall or non-existent leak rate. For hermetically sealed packages it istypically favorable to backfill the packaging of a combination of oxygenand nitrogen such as clean dry air (CDA), but can be others such asnitrogen. Typically for GaN based lasers it is desirable forhermetically sealed packages, but other packages can be considered anddeployed for various applications. Examples of off the shelf packagesfor the CPoS white light source include TO cans such as TO38, TO56, TO9,TO5, or TO46. Flat packages configured with windows can also be used.Examples of flat packages include a butterfly package like a TOSA.Surface mount device (SMD) packages can also be used, which areattractive due to their low price, hermetic sealing, and potentially lowthermal impedance. In other embodiments, custom packages are used.

As an example, the package has a low profile and may include a flat packceramic multilayer or single layer. The layer may include a copper, acopper tungsten base such as butterfly package or covered CT mount,Q-mount, or others. In a specific embodiment, the laser devices aresoldered on CTE matched material with low thermal resistance (e.g., AlN,diamond, diamond compound) and forms a sub-assembled chip on ceramics.The sub-assembled chip is then assembled together on a second materialwith low thermal resistance such as copper including, for example,active cooling (i.e., simple water channels or micro channels), orforming directly the base of the package equipped with all connectionssuch as pins. The flatpack is equipped with an optical interface such aswindow, free space optics, connector or fiber to guide the lightgenerated and a cover environmentally protective.

FIG. 29 presents a schematic illustration of one example of a packagedCPoS white light source according to the present invention. In thisexample, a transmission mode white light source is configured in aTO-can type package. The TO-can has a base member 501 with a protrudingpedestal member 502, wherein the pedestal member is configured totransmit heat from the pedestal to the base where the heat issubsequently passed to a heat sink. The base member can be comprised ofa metal such as copper, copper tungsten, aluminum, or steel, or other.The transmissive white light source 503 according to this invention ismounted on the pedestal 502. The mounting to the pedestal can beaccomplished using a soldering or gluing technique such as using AuSnsolders, SAC solders, lead containing solders, indium, or other solders.Electrical connections from the p-electrode and n-electrode of the laserdiode are made using wire bonds 504 and 505. The wirebonds connect theelectrode to electrical feedthroughs 506 and 507 that are electricallyconnected to external pins 508 and 509 on the backside of the TO-canbase. The pins are then electrically coupled to a power source toelectrify the white light source and generate white light emission. Inthis configuration the white light source is not capped or sealed suchthat is exposed to the open environment. Of course, the example in FIG.29 is merely an example and is intended to illustrate one possiblesimple configuration of a packaged CPoS white light source.Specifically, since can-type packages are widely popular for laserdiodes and are available off the shelf they could be one option for alow cost and highly adaptable solution.

FIG. 30 is a schematic illustration of the CPoS white light sourceconfigured in a can type package as shown in FIG. 29, but with anadditional cap member to form a seal around the white light source. Asseen in FIG. 30, the TO-can type package 501 has a cap 502 mounted tothe base. The cap can be soldered, brazed, welded, or glue to the base.The cap member has a transparent window region 503 configured to allowthe emitted white light to pass to the outside environment where it canbe harnessed in application. The sealing type can be an environmentalseal or a hermetic seal, and in an example the sealed package isbackfilled with a nitrogen gas or a combination of a nitrogen gas and anoxygen gas. In some embodiments, a lens or other type of optical elementto shape, direct, or collimate the white light is included directly inthe cap member. Of course, the example in FIG. 30 is merely an exampleand is intended to illustrate one possible configuration of sealing awhite light source. Specifically, since TO-can type packages are easilyhermetically sealed, this embodiment may be suitable for applicationswhere hermetic seals are needed.

An alternative example of a packaged CPoS white light source accordingto the present invention is provided in the schematic diagram of FIG.31. In this example, a reflective mode white light source is configuredin a surface mount device (SMD) type package. The example SMD packagehas a base member 501 with the reflective mode white light source 502mounted on the base member wherein the base member is configured toconduct heat away from the white light source and to a heat sink. Thebase member is comprised of a thermally conductive material such ascopper, copper tungsten, aluminum, SiC, steel, diamond, compositediamond, AlN, sapphire, or other metals, ceramics, or semiconductors.The mounting to the base member can be accomplished using a soldering orgluing technique such as using AuSn solders, SAC solders, leadcontaining solders, indium, or other solders. The mounting joint couldalso be formed from thermally conductive glues, thermal epoxies, andother materials. Electrical connections from the p-electrode andn-electrode of the laser diode are made to using wirebonds 503 and 504to internal feedthroughs 505 and 506. The feedthroughs are electricallycoupled to external leads such as 507. The external leads can beelectrically coupled to a power source to electrify the white lightsource and generate white light emission. The top surface 508 of thesurface mount package may be comprised of or coated with a reflectivelayer to prevent or mitigate any losses relating from downward directedor reflected light. Moreover, all surfaces within the package includingthe laser diode member and submount member may be enhanced for increasedreflectivity to help improve the useful white light output. In thisconfiguration the white light source is not capped or sealed such thatis exposed to the open environment. Of course, the example is FIG. 31 ismerely an example and is intended to illustrate one possible simpleconfiguration of a surface mount packaged CPoS white light source.Specifically, since surface mount type packages are widely popular forLEDs and other devices and are available off the shelf they could be oneoption for a low cost and highly adaptable solution.

FIG. 32 is a schematic illustration of the CPoS white light sourceconfigured in a SMD type package as shown in FIG. 31, but with anadditional cap member to form a seal around the white light source. Asseen in FIG. 32, the SMD type package has a base member 501 with thewhite light source 502 mounted to the base. The mounting to the base canbe accomplished using a soldering or gluing technique such as using AuSnsolders, SAC solders, lead containing solders, indium, or other solders.Overlying the white light source is a cap member 503, which is attachedto the base member around the sides. In an example, the attachment canbe a soldered attachment, a brazed attachment, a welded attachment, or aglued attachment to the base member. The cap member has at least atransparent window region and in preferred embodiments would beprimarily comprised of a transparent window region such as thetransparent dome cap illustrated in FIG. 32. The transparent materialcan be a glass, a quartz, sapphire, silicon carbide, diamond, plastic,or any suitable transparent material. The sealing type can be anenvironmental seal or a hermetic seal, and in an example the sealedpackage is backfilled with a nitrogen gas or a combination of a nitrogengas and an oxygen gas. Electrical connections from the p-electrode andn-electrode of the laser diode are made using wire bonds 504 and 505.The wirebonds connect the electrode to electrical feedthroughs 506 and507 that are electrically connected to external leads such as 508 on theoutside of the sealed SMD package. The leads are then electricallycoupled to a power source to electrify the white light source andgenerate white light emission. In some embodiments, a lens or other typeof optical element to shape, direct, or collimate the white light isincluded directly in the cap member. Of course, the example in FIG. 32is merely an example and is intended to illustrate one possibleconfiguration of sealing a white light source. Specifically, since SMDtype packages are easily hermetically sealed, this embodiment may besuitable for applications where hermetic seals are needed.

In all embodiments, transmissive and reflective mode, of the integratedCPoS white light source according to the present invention safetyfeatures and design considerations can be included. In any based laserbased source, safety is a key aspect. It is critical that the lightsource cannot be compromised or modified in such a way to create laserdiode beam that can be harmful to human beings, animals, or theenvironment. Thus, the overall design should include safetyconsiderations and features, and in some cases even active componentsfor monitoring. Examples of design considerations and features forsafety include positioning the laser beam with respect to the phosphorin a way such that if the phosphor is removed or damaged, the exposedlaser beam would not make it to the outside environment in a harmfulform such as collimated, coherent beam. More specifically, the whitelight source is designed such that laser beam is pointing away from theoutside environment and toward a surface or feature that will preventthe beam from being reflected to the outside world. In an example of apassive design features for safety include beam dumps and/or absorbingmaterial can be specifically positioned in the location the laser beamwould hit in the event of a removed or damaged phosphor.

In one embodiment, an optical beam dump serves as an optical element toabsorb the laser beam that could otherwise be dangerous to the outsideenvironment. Design concerns in the beam dump would include themanagement and reduction of laser beam back reflections and scatteringas well as dissipation of heat generated by absorption. Simple solutionswhere the optical power is not too high, the absorbing material can beas simple as a piece of black velvet or flock paper attached to abacking material with a glue, solder, or other material. In high powerapplications such as those that would incorporated into high power lasersystems, beam dumps must often incorporate more elaborate features toavoid back-reflection, overheating, or excessive noise. Dumping thelaser beam with a simple flat surface could result in unacceptably largeamounts of light escaping to the outside world where it could bedangerous to the environment even though the direct reflection ismitigated. One approach to minimize scattering is to use a porous ordeep dark cavity material deep lined with an absorbing material to dumpthe beam.

A commonly available type of beam dump suitable for most medium-powerlasers is a cone of aluminum with greater diameter than the beam,anodized to a black color and enclosed in a canister with a black,ribbed interior. Only the point of the cone is exposed to the beamhead-on; mostly, incoming light grazes the cone at an angle, which easesperformance requirements. Any reflections from this black surface arethen absorbed by the canister. The ribs both help to make light lesslikely to escape, and improve heat transfer to the surrounding air REF.[https://en.wikipedia.org/wiki/Beam_dump].

An example of a packaged CPoS white light source including a beam dumpsafety feature according to the present invention is provided in theschematic diagram of FIG. 33. In this example, a reflective mode whitelight source is configured in a surface mount device (SMD) type package.The example SMD package has a base member 501 with the reflective modewhite light source 502 mounted on the base member wherein the basemember is configured to conduct heat away from the white light sourceand to a heat sink. The base member is comprised of a thermallyconductive material such as copper, copper tungsten, aluminum, SiC,steel, diamond, composite diamond, AlN, sapphire, or other metals,ceramics, or semiconductors The mounting to the base member can beaccomplished using a soldering or gluing technique such as using AuSnsolders, SAC solders, lead containing solders, indium, or other solders.The joint could also be formed from thermally conductive glues, thermalepoxies such as silver epoxy, thermal adhesives, and other materials.Alternatively the joint could be formed from a metal-metal bond such asa Au—Au bond. Electrical connections from the p-electrode andn-electrode of the laser diode are made to using wirebonds 503 and 504to internal feedthroughs 505 and 506. The feedthroughs are electricallycoupled to external leads such as 507. The external leads can beelectrically coupled to a power source to electrify the white lightsource and generate white light emission. The example beam 508 isconfigured in the optical pathway of the laser diode in an event thephosphor were damage or removed and the laser beam was reflecting fromthe support member of the phosphor. In this example, the beam dump isshaped like a cube, but this is just an example and the shape, size, andlocation of the beam dump would be optimized based on providing thesafety function while not unacceptably comprising efficiency of thewhite light source. In this example, the face of the beam dumpconfigured to be in the optical pathway of the reflected beam could beconfigured from a porous material with deep cavities that propagatethrough the cube beam dump. Additionally, the beam dump could becomprised of an absorbing to absorb the laser beam and the beam is wellheat sunk to the package member and a heat sink to dissipate the thermalenergy generated during the absorption of the laser beam. The sides ofthe beam dump member 508 not positioned in the laser beam pathway couldbe comprised of a reflective material to increase the useful outputwhite light. Moreover, all surfaces within the package including thelaser diode member and submount member may be enhanced for increasedreflectivity to help improve the useful white light output. In thisconfiguration the white light source is not capped or sealed such thatis exposed to the open environment. Of course, the example in FIG. 33 ismerely an example and is intended to illustrate one possible simpleconfiguration of a packaged CPoS white light source with a built insafety feature. In other embodiments more than one safety feature can beincluded, a safety system comprised of multiple safety elements can beincluded, and such safety systems can be comprised of active and passivesafety elements. Moreover, the safety elements or safety systems can beincluded in other packages included flat packages, custom packages, orcan-type packages.

Of course, optical beam dumps is just one example of a laser safetyfeature, but there can be many others. Generally, the laser diode shouldnot be configured to point toward the outside environment such that ifthere is a damaging or tampering event the direct laser will not escapeto the outside world.

In some embodiments of this invention, safety features and systems useactive components. Example active components includephotodetectors/photodiode and thermistors. A photodiode is asemiconductor device that converts light into current wherein a currentis generated when light within a certain wavelength range is incident onthe photodiode. A small amount of current is also produced when no lightis present. Photodiodes may be combined with components such as opticalfilters to provide a wavelength or polarization selection of the lightincident on the detector, built-in lenses to focus the light ormanipulate the light incident on the detector, and may have large orsmall surface areas to select a certain responsivity and/or noise level.The most prevalent photodiode type is based on Si as the opticalabsorbing material, wherein a depletion region is formed. When a photonis absorbed in this region an electron-hole pair is formed, whichresults in a photocurrent. The primary parameter defining thesensitivity of a photodiode is its quantum efficiency, (QE) which isdefined as the percentage of incident photons generating electron-holepairs which subsequently contribute to the output signal. Quantumefficiencies of about 80% are usual for silicon detectors operating atwavelengths in the 800-900 nm region. The sensitivity of a photodiodemay also be expressed in units of amps of photodiode current per watt ofincident illumination. This relationship leads to a tendency forresponsivity to reduce as the wavelength becomes shorter. For example,at 900 nm, 80% QE represents a responsivity of 0.58 A/W, whereas at 430nm, the same QE gives only 0.28 A/W. In alternative embodiments,photodiodes based on other materials such as Ge, InGaAs, GaAs, InGaAsP,InGaN, GaN, InP, or other semiconductor based materials can be used. Thephotodiode can be a p-n type, a p-i-n type, an avalanche photodiode, auni-traveling carrier photodiode, a partially depleted photodiode, orother type of diode.

The decreasing responsivity with such shorter wavelengths presentsdifficulty in achieving a high performance silicon based photodiode inthe violet or blue wavelength range. To overcome this difficulty blueenhancement and/or filter techniques can be used to improve theresponsivity this wavelength range. However, such techniques can lead toincreased costs, which may not be compatible with some applications.Several techniques can be used to overcome this challenge includingdeploying new technologies for blue enhanced silicon photodiodes orusing photodiodes based on different material systems such asphotodiodes based on GaN/InGaN. In one embodiment an InGaN and/orGaN-containing photodiode is combined with the integrated white lightsource. In a specific embodiment, the photodiode is integrated with thelaser diode either by a monolithic technique or by an integration onto acommon submount or support member as the laser diode to form anintegrated GaN/InGaN based photodiode.

In another embodiment of this invention to overcome the difficulty ofachieving a low cost silicon based photodiode operable with highresponsivity in the blue wavelength region, a wavelength convertermaterial such as a phosphor can be used to down convert ultraviolet,violet, or blue laser light to a wavelength more suitable forhigh-responsivity photo-detection according to the criteria required inan embodiment for this invention. For example, if photodiodes operatingin the green, yellow, or red wavelength regime can be lower cost andhave a suitable responsivity for the power levels associated with aconverted wavelength, the photodiode can be coated with phosphors toconvert the laser light to a red, green, or yellow emission. In otherembodiments the detectors are not coated, but a converter member such asa phosphor is place in the optical pathway of the laser beam orscattered laser beam light and the photodiode.

Strategically located detectors designed to detect direct blue emissionfrom the laser, scattered blue emission, or phosphor emission such asyellow phosphor emission can be used to detect failures of the phosphorwhere a blue beam could be exposed or other malfunctions of the whitelight source. Upon detection of such an event, a close circuit orfeedback loop would be configured to cease power supply to the laserdiode and effectively turn it off.

As an example, a photodiode can be used to detect phosphor emissioncould be used to determine if the phosphor emission rapidly reduced,which would indicate that the laser is no longer effectively hitting thephosphor for excitation and could mean that the phosphor was removed ordamaged. In another example of active safety features, a blue sensitivephotodetector could be positioned to detect reflected or scatter blueemission from the laser diode such that if the phosphor was removed orcompromised the amount of blue light detected would rapidly increase andthe laser would be shut off by the safety system.

In a preferred embodiment, a InGaN/GaN-based photodiode is integratedwith the white light source. The InGaN/GaN-based photodiode can beintegrated using a discrete photodiode mounted in the package or can bedirectly integrated onto a common support member with the laser diode.In a preferable embodiment, the InGaN/GaN-based photodiode can bemonolithically integrated with the laser diode.

In yet another example of active safety features a thermistor could bepositioned near or under the phosphor material to determine if there wasa sudden increase in temperature which may be a result of increaseddirect irradiation from the blue laser diode indicating a compromised orremoved phosphor. Again, in this case the thermistor signal would tripthe feedback loop to cease electrical power to the laser diode and shutit off.

In many applications according to the present invention, the packagedintegrated white light source will be attached to a heat sink member.The heat sink is configured to transfer the thermal energy from thepackaged white light source to a cooling medium. The cooling medium canbe an actively cooled medium such as a thermoelectric cooler or amicrochannel cooler, or can be a passively cooled medium such as anair-cooled design with features to maximize surface and increase theinteraction with the air such as fins, pillars, posts, sheets, tubes, orother shapes. The heat sink will typically be formed from one or moremetal members, but can be others such as thermally conductive ceramics,semiconductors, or composites.

The heat sink member is configured to transport thermal energy from thepackaged laser diode based white light source to a cooling medium. Theheat sink member can be comprised of a metal, ceramic, composite,semiconductor, plastic and is preferably comprised of a thermallyconductive material. Examples of candidate materials include copperwhich may have a thermal conductivity of about 400 W/(mK), aluminumwhich may have a thermal conductivity of about 200 W/(mK), 4H-SiC whichmay have a thermal conductivity of about 370 W/(mK), 6H-SiC which mayhave a thermal conductivity of about 490 W/(mK), AlN which may have athermal conductivity of about 230 W/(mK), a synthetic diamond which mayhave a thermal conductivity of about >1000 W/(mK), a composite diamond,sapphire, or other metals, ceramics, composites, or semiconductors. Theheat sink member may be formed from a metal such as copper, coppertungsten, aluminum, or other by machining, cutting, trimming, ormolding.

The attachment joint joining the packaged white light source accordingto this invention to the heat sink member should be carefully designedand processed to minimize the thermal impedance. Therefore a suitableattaching material, interface geometry, and attachment process practicemust be selected for an appropriate thermal impedance with sufficientattachment strength. Examples include AuSn solders, SAC solders, leadcontaining solders, indium solders, indium, and other solders. The jointcould also be formed from thermally conductive glues, thermal epoxiessuch as silver epoxy, thermal adhesives, and other materials.Alternatively the joint could be formed from a metal-metal bond such asa Au—Au bond. The common support member with the laser and phosphormaterial is configured to provide thermal impedance of less than 10degrees Celsius per watt or less than 5 degrees Celsius per watt ofdissipated power characterizing a thermal path from the laser device toa heat sink.

FIG. 34 is a schematic illustration of a CPoS white light sourceconfigured in a sealed SMD mounted on a heat sink member according tothe present invention. The sealed white light source in an SMD packageis similar to that example shown in FIG. 32. As seen in FIG. 36, the SMDtype package has a base member 601 with the white light source 602mounted to the base and a cap member 603 providing a seal for the lightsource. The mounting to the base can be accomplished using a solderingor gluing technique such as using AuSn solders, SAC solders, leadcontaining solders, indium, or other solders. The cap member has atleast a transparent window region. The transparent material can be aglass, a quartz, sapphire, silicon carbide, diamond, plastic, or anysuitable transparent material. The base member of the SMD package isattached to a heat sink member 604. The heat sink member can becomprised of a material such as a metal, ceramic, composite,semiconductor, or plastic and is preferably comprised of a thermallyconductive material. Examples of candidate materials include aluminum,copper, copper tungsten, steel, SiC, AlN, diamond, a composite diamond,sapphire, or other materials. Of course, the example in FIG. 34 ismerely an example and is intended to illustrate one possibleconfiguration of a white light source according to the present inventionmounted on a heat sink. Specifically, the heat sink could includefeatures to help transfer heat such as fins.

In some embodiments of this invention, the CPoS integrated white lightsource is combined with one or more optical members to manipulate thegenerated white light. In an example the white light source could servein a spot light system such as a flashlight or an automobile headlamp orother light applications where the light must be directed or projectedto a specified location or area. As an example, to direct the light itshould be collimated such that the photons comprising the white lightare propagating parallel to each other along the desired axis ofpropagation. The degree of collimation depends on the light source andthe optics using to collimate the light source. For the highestcollimation a perfect point source of light with 4 pi emission and asub-micron or micron-scale diameter is desirable. In one example, thepoint source is combined with a parabolic reflector wherein the lightsource is placed at the focal point of the reflector and the reflectortransforms the spherical wave generated by the point source into acollimated beam of plane waves propagating along an axis.

In one embodiment a reflector is coupled to the white light source.Specifically, a parabolic (or paraboloid or paraboloidal) reflector isdeployed to project the white light. By positioning the white lightsource in the focus of a parabolic reflector, the plane waves will bereflected and propagate as a collimated beam along the axis of theparabolic reflector.

In an another example a simple singular lens or system of lenses is usedto collimate the white light into a projected beam. In a specificexample, a single aspheric lens is place in front of the phosphor memberemitting white light and configured to collimate the emitted whitelight. In another embodiment, the lens is configured in the cap of thepackage containing the integrated white light source. In someembodiments, a lens or other type of optical element to shape, direct,or collimate the white light is included directly in the cap member Inan example the lens is comprised of a transparent material such as aglass, SiC, sapphire, quartz, a ceramic, a composite, or asemiconductor.

Such white light collimating optical members can be combined with thewhite light source at various levels of integration. For example, thecollimating optics can reside within the same package as the integratedwhite light source in a co-packaged configuration. In a further level ofintegration the collimating optics can reside on the same submount orsupport member as the white light source. In another embodiment, thecollimating optics can reside outside the package containing theintegrated white light source.

In one embodiment according to the present invention, a reflective modeintegrated white light source is configured in a flat type package witha lens member to create a collimated white beam as illustrated in FIG.36. As seen in FIG. 35, the flat type package has a base or housingmember 601 with a collimated white light source 602 mounted to the baseand configured to create a collimated white beam to exit a window 603configured in the side of the base or housing member. The mounting tothe base or housing can be accomplished using a soldering or gluingtechnique such as using AuSn solders, SAC solders, lead containingsolders, indium, or other solders. Electrical connections to the whitelight source can be made with wire bonds to the feedthroughs 604 thatare electrically coupled to external pins 605. In this example, thecollimated reflective mode white light source 602 comprises the laserdiode 606, the phosphor wavelength converter 607 configured to acceptthe laser beam, and a collimating lens such as an aspheric lens 608configured in front of the phosphor to collect the emitted white lightand form a collimated beam. The collimated beam is directed toward thewindow 603 wherein the window region is formed from a transparentmaterial. The transparent material can be a glass, quartz, sapphire,silicon carbide, diamond, plastic, or any suitable transparent material.The external pins 605 are electrically coupled to a power source toelectrify the white light source and generate white light emission. Asseen in the Figure, any number of pins can be included on the flat pack.In this example there are 6 pins and a typical laser diode driver onlyrequires 2 pins, one for the anode and one for the cathode. Thus, theextra pins can be used for additional elements such as safety featureslike photodiodes or thermistors to monitor and help control temperature.Of course, the example in FIG. 35 is merely an example and is intendedto illustrate one possible configuration of sealing a white lightsource.

In one embodiment according to the present invention, a transmissivemode integrated white light source is configured in a flat type packagewith a lens member to create a collimated white beam as illustrated inFIG. 36. As seen in FIG. 36, the flat type package has a base or housingmember 601 with a collimated white light source 602 mounted to the baseand configured to create a collimated white beam to exit a window 603configured in the side of the base or housing member. The mounting tothe base or housing can be accomplished using a soldering or gluingtechnique such as using AuSn solders, SAC solders, lead containingsolders, indium, or other solders. Electrical connections to the whitelight source can be made with wire bonds to the feedthroughs 604 thatare electrically coupled to external pins 605. In this example, thecollimated transmissive mode white light source 602 comprises the laserdiode 606, the phosphor wavelength converter 607 configured to acceptthe laser beam, and a collimating lens such as an aspheric lens 608configured in front of the phosphor to collect the emitted white lightand form a collimated beam. The collimated beam is directed toward thewindow 603 wherein the window region is formed from a transparentmaterial. The transparent material can be a glass, quartz, sapphire,silicon carbide, diamond, plastic, or any suitable transparent material.The external pins 605 are electrically coupled to a power source toelectrify the white light source and generate white light emission. Asseen in the Figure, any number of pins can be included on the flat pack.In this example there are 6 pins and a typical laser diode driver onlyrequires 2 pins, one for the anode and one for the cathode. Thus, theextra pins can be used for additional elements such as safety featureslike photodiodes or thermistors to monitor and help control temperature.Of course, the example in FIG. 36 is merely an example and is intendedto illustrate one possible configuration of sealing a white lightsource.

The flat type package examples shown in FIGS. 35 and 36 according to thepresent invention are illustrated in an unsealed configuration without alid to show examples of internal configurations. However, flat packagesare easily sealed with a lid or cap member. FIG. 37 is an example of asealed flat package with a collimated white light source inside. As seenin FIG. 37, the flat type package has a base or housing member 601 withexternal pins 602 configured for electrical coupling to internalcomponents such as the white light source, safety features, andthermistors. The sealed flat package is configured with a window 603 forthe collimated white beam to exit and a lid or cap 604 to form a sealbetween the external environment and the internal components. The lid orcap can be soldered, brazed, welded, glued to the base, or other. Thesealing type can be an environmental seal or a hermetic seal, and in anexample the sealed package is backfilled with a nitrogen gas or acombination of a nitrogen gas and an oxygen gas.

FIG. 38 presents a schematic diagram illustrating a transmissivephosphor embodiment of an integrated white light source including awhite light collimating optic according to the present invention. Inthis embodiment the gallium and nitrogen containing lift-off andtransfer technique is deployed to fabricate a very small and compactsubmount member with the laser diode chip formed from transferredepitaxy layers. Of course, a conventional chip on submount embodimentsuch as that shown in FIG. 4 and in FIG. 11 could be used for thisintegrated collimated white light embodiment. The laser based CPoS whitelight device is comprised of submount material 601 that serves as thecommon support member configured to act as an intermediate materialbetween a laser diode 602 formed in transferred gallium and nitrogencontaining epitaxial layers and a final mounting surface and as anintermediate material between the phosphor plate material 605 and afinal mounting surface. The laser diode and/or submount is configuredwith electrodes 603 and 604 that may be formed with deposited metallayers and combination of metal layers including, but not limited to Au,Pd, Pt, Ni, Al, titanium, or others. Wirebonds can be configured tocouple the electrical power to the electrodes 603 and 604 on the laserdiode. The laser beam 606 is incident on the phosphor to form a white alight exiting the phosphor. The white light exiting the phosphor memberis coupled into a lens such as an aspheric lens 607 for collimation andbeam shaping. The electrodes 603 and 604 are configured for anelectrical connection to an external power source such as a laserdriver, a current source, or a voltage source. Wirebonds can be formedon the electrodes to couple electrical power to the laser diode deviceto generate a laser beam output from the laser diode. Of course this ismerely an example of a configuration with an integrated collimatingoptic and there could be many variants on this embodiment includingusing a conventional chip on submount configuration as shown in FIG. 4for integration of the collimation optic with the laser diode andphosphor. In other alternatives phosphors with different sizes andshapes can be used, different geometrical designs of the submount orcommon support member can be used, different orientations of the laseroutput beam with respect to the phosphor can be deployed, and differentelectrode and electrical designs can be implemented, and others.

FIG. 39 presents a schematic diagram illustrating a reflective modephosphor embodiment of an integrated white light source according toFIG. 25, but also including a reflector optic such as a parabolicreflector to collimate the white light according to the presentinvention. In this embodiment the gallium and nitrogen containing laserdiode 601 or chip on submount is mounted on a common support member 602which could be the submount member for the laser diode. The commonsupport member also supports the phosphor member 603 configured to belocated in the pathway of the laser diode output beam 604, wherein thelaser diode beam can excite the phosphor and emit a white light. Areflector member 605 such as a parabolic reflector is positioned withrespect to the primary emission surface of the phosphor member such thatthe phosphor member is near the focal point of the reflector. Thereflector is configured to collect the white emission from the phosphorand collimate it into a beam of white light projected along an axis 606.The reflector member is configured with an opening or other entry forthe laser beam 604 to enter inside the reflector to interact with thephosphor. In other alternatives phosphors with different sizes andshapes can be used, different geometrical designs of the submount orcommon support member can be used, different orientations of the laseroutput beam with respect to the phosphor can be deployed, differentcollimation optics or other optics can be used, and different electrodeand electrical designs can be implemented, and others.

FIG. 40 presents a schematic diagram illustrating a reflective modephosphor embodiment of an integrated white light source according toFIG. 28, but also including a lens such as an aspheric lens to collimatethe white light according to the present invention. In this embodimentthe gallium and nitrogen containing laser diode 601 or chip on submountis mounted on a common support member 602 which could be the submountmember for the laser diode. The common support member also supports thephosphor member 603 configured to be located in the pathway of the laserdiode output beam 604, wherein the laser diode beam can excite thephosphor and emit a white light. A lens member 605 such as an asphericlens is positioned in front of or above the primary emission surfacefrom the phosphor member. The lens is configured to collect the whiteemission from the phosphor and collimate it into a beam of white lightprojected along an axis 606. The lens member is supported by amechanical support member, which can be an additional member 607 or canbe supported directly by the common support member. In otheralternatives phosphors with different sizes and shapes can be used,different geometrical designs of the submount or common support membercan be used, different orientations of the laser output beam withrespect to the phosphor can be deployed, different collimation optics orother optics can be used, and different electrode and electrical designscan be implemented, and others.

FIG. 41 is a schematic illustration of the CPoS white light sourceconfigured in a can type package as shown in FIG. 30, but with anadditional reflector member configured to collimate and project thewhite light. The example configuration for a collimated white light fromTO-can type package according to FIG. 42 comprises a TO-can base 601, acap configured with a transparent window region 602 mounted to the base.The cap can be soldered, brazed, welded, or glue to the base. Areflector member 603 is configured outside the window region wherein thereflector functions to capture the emitted white light passing thewindow, collimate the light, and then project it along the axis 604. Ofcourse, this is merely an example and is intended to illustrate onepossible configuration of combining the integrated CPoS white lightsource according to this invention with a collimation optic. In anotherexample, the reflector could be integrated into the window member of thecap or be included within the TO package member.

In an alternative embodiment, FIG. 42 provides a schematic illustrationof the CPoS white light source configured in a can type package as shownin FIG. 30, but with an additional lens member configured to collimateand project the white light. The example configuration for a collimatedwhite light from TO-can type package according to FIG. 42 comprises aTO-can base 601, a cap configured with a transparent window region 602mounted to the base. The cap can be soldered, brazed, welded, or glue tothe base. An aspheric lens member 603 configured outside the windowregion wherein the lens functions to capture the emitted white lightpassing the window, collimate the light, and then project it along theaxis 604. Of course, this is merely an example and is intended toillustrate one possible configuration of combining the integrated whitelight source according to this invention with a collimation optic. Inanother example, the collimating lens could be integrated into thewindow member on the cap or could be included within the package member.

In an alternative embodiment, FIG. 43 provides a schematic illustrationof a white light source according to this invention configured in anSMD-type package as shown in FIG. 32, but with an additional parabolicmember configured to collimate and project the white light. The exampleconfiguration for a collimated white light from SMD-type packageaccording to FIG. 43 comprises an SMD type package 601 comprising abased and a cap or window region and the integrated white light source602. The SMD package is mounted to a heat-sink member 603 configured totransport and/or store the heat generated in the SMD package from thelaser and phosphor member. A reflector member 604 such as a parabolicreflector is configured with the white light emitting phosphor member ofthe white light source at or near the focal point of the parabolicreflector. The parabolic reflector functions to collimate and projectthe white light along the axis of projection 605. Of course, this ismerely an example and is intended to illustrate one possibleconfiguration of combining the integrated white light source accordingto this invention with a reflector collimation optic. In anotherexample, the collimating reflector could be integrated into the windowmember of the cap or could be included within the package member. In apreferred embodiment, the reflector is integrated with or attached tothe submount.

In an alternative embodiment, FIG. 44 provides a schematic illustrationof a white light source according to this invention configured in anSMD-type package as shown in FIG. 32, but with an additional lens memberconfigured to collimate and project the white light. The exampleconfiguration for a collimated white light from SMD-type packageaccording to FIG. 44 comprises an SMD type package 601 comprising abased and a cap or window region and the integrated white light source602. The SMD package is mounted to a heat-sink member 603 configured totransport and/or store the heat generated in the SMD package from thelaser and phosphor member. A lens member 604 such as an aspheric lens isconfigured with the white light emitting phosphor member of the whitelight source to collect and collimate a substantial portion of theemitted white light. The lens member is supported by support members 605to mechanically brace the lens member in a fixed position with respectto the white light source. The support members can be comprised ofmetals, plastics, ceramics, composites, semiconductors or other. Thelens member functions to collimate and project the white light along theaxis of projection 606. Of course, this is merely an example and isintended to illustrate one possible configuration of combining theintegrated white light source according to this invention with areflector collimation optic. In another example, the collimatingreflector could be integrated into the window member of the cap or couldbe included within the package member. In a preferred embodiment, thereflector is integrated with or attached to the submount.

In an embodiment according to the present invention, FIG. 45 provides aschematic illustration of a white light source according to thisinvention configured in an SMD-type package as shown in FIG. 32, butwith an additional lens member and reflector member configured tocollimate and project the white light. The example configuration for acollimated white light from SMD-type package according to FIG. 45comprises an SMD type package 601 comprising a based and a cap or windowregion and the integrated white light source 602. The SMD package ismounted to a heat-sink member 603 configured to transport and/or storethe heat generated in the SMD package from the laser and phosphormember. A lens member 604 such as an aspheric lens is configured withthe white light source to collect and collimate a substantial portion ofthe emitted white light. A reflector housing 605 or lens member isconfigured between the white light source and the lens member to reflectany stray light or light that would not otherwise reach the lens memberinto the lens member for collimation and contribution to the collimatedbeam. In one embodiment the lens member is supported by the reflectorhousing member to mechanically brace the lens member in a fixed positionwith respect to the white light source. The lens member functions tocollimate and project the white light along the axis of projection 606.Of course, this is merely an example and is intended to illustrate onepossible configuration of combining the integrated white light sourceaccording to this invention with a reflector collimation optic. Inanother example, the collimating reflector could be integrated into thewindow member of the cap or could be included within the package member.In a preferred embodiment, the reflector is integrated with or attachedto the submount.

A further understanding of the nature and advantages of the presentinvention may be realized by reference to the latter portions of thespecification and attached drawings.

In all of the side pumped and transmissive and reflective embodiments ofthis invention the additional features and designs can be included. Forexample shaping of the excitation laser beam for optimizing the beamspot characteristics on the phosphor can be achieved by careful designconsiderations of the laser beam incident angle to the phosphor or withusing integrated optics such as free space optics like collimating lens.Safety features can be included such as passive features like physicaldesign considerations and beam dumps and/or active features such asphotodetectors or thermistors that can be used in a closed loop to turnthe laser off when a signal is indicated. Moreover, optical elements canbe included to manipulate the generated white light. In some embodimentsreflectors such as parabolic reflectors or lenses such as collimatinglenses are used to collimate the white light or create a spot light thatcould be applicable in an automobile headlight, flashlight, spotlight,or other lights.

In one embodiment, the present invention provides a laser-based whitelight source comprising a form factor characterized by a length, awidth, and a height. The apparatus has a support member and at least onegallium and nitrogen containing laser diode devices and phosphormaterial overlying the support member. The laser device is capable of anemission of a laser beam with a wavelength preferably in the blue regionof 425 nm to 475 nm or in the ultra violet or violet region of 380 nm to425 nm, but can be other such as in the cyan region of 475 nm to 510 nmor the green region of 510 nm to 560 nm. In a preferred embodiment thephosphor material can provide a yellowish emission in the 560 nm to 580nm range such that when mixed with the blue emission of the laser diodea white light is produced. In other embodiments phosphors with red,green, yellow, and even blue emission can be used in combination withthe laser diode excitation source to produce a white light with colormixing. The apparatus typically has a free space with a non-guided laserbeam characteristic transmitting the emission of the laser beam from thelaser device to the phosphor material. The laser beam spectral width,wavelength, size, shape, intensity, and polarization are configured toexcite the phosphor material. The beam can be configured by positioningit at the precise distance from the phosphor to exploit the beamdivergence properties of the laser diode and achieve the desired spotsize. In other embodiments free space optics such as collimating lensescan be used to shape the beam prior to incidence on the phosphor. Thebeam can be characterized by a polarization purity of greater than 60%and less than 100%. As used herein, the term “polarization purity” meansgreater than 50% of the emitted electromagnetic radiation is in asubstantially similar polarization state such as the transverse electric(TE) or transverse magnetic (TM) polarization states, but can have othermeanings consistent with ordinary meaning. In an example, the laser beamincident on the phosphor has a power of less than 0.1 W, greater than0.1 W, greater than 0.5 W, greater than 1 W, greater than 5 W, greaterthan 10 W, or greater than 10 W. The phosphor material is characterizedby a conversion efficiency, a resistance to thermal damage, a resistanceto optical damage, a thermal quenching characteristic, a porosity toscatter excitation light, and a thermal conductivity. In a preferredembodiment the phosphor material is comprised of a yellow emitting YAGmaterial doped with Ce with a conversion efficiency of greater than 100lumens per optical watt, greater than 200 lumens per optical watt, orgreater than 300 lumens per optical watt, and can be a polycrystallineceramic material or a single crystal material. The white light apparatusalso has an electrical input interface configured to couple electricalinput power to the laser diode device to generate the laser beam andexcite the phosphor material. The white light source configured toproduce greater than 1 lumen, 10 lumens, 100 lumens, 1000 lumens, orgreater of white light output. The support member is configured totransport thermal energy from the at least one laser diode device andthe phosphor material to a heat sink. The support member is configuredto provide thermal impedance of less than 10 degrees Celsius per watt orless than 5 degrees Celsius per watt of dissipated power characterizinga thermal path from the laser device to a heat sink. The support memberis comprised of a thermally conductive material such as copper, coppertungsten, aluminum, SiC, sapphire, AlN, or other metals, ceramics, orsemiconductors.

According to an embodiment, the present invention provides a dynamiclaser-based light source or light projection apparatus including amicro-display such as a microelectromechanical system (MEMS) scanningmirror, or “flying mirror” or a digital light processing (DLP) chip todynamically modify the spatial pattern and/or the color of the emittedlight. In one embodiment the light is pixelated to activate certainpixels and not activate other pixels to form a spatial pattern or imageof white light. In another example, the dynamic light source isconfigured for steering or pointing the light beam. The steering orpointing can be accomplished by a user input configured from a dial,switch, or joystick mechanism or can be directed by a feedback loopincluding sensors.

According to an embodiment, the present invention provides a dynamiclaser-based light source or light projection apparatus including ahousing having an aperture. The apparatus can include an input interfacefor receiving a signal to activate the dynamic feature of the lightsource. The apparatus can include a video or signal processing module.Additionally, the apparatus includes a light source based on a lasersource. The laser source includes one or more of a violet laser diode orblue laser diode. The dynamic light feature output comprised from aphosphor emission excited by the output beam of a laser diode, or acombination of a laser diode and a phosphor member. The violet or bluelaser diode is fabricated on a polar, nonpolar, or semipolar orientedGa-containing substrate. The apparatus can include amicroelectromechanical system (MEMS) scanning mirror, or “flyingmirror”, configured to project the laser light or laser pumped phosphorwhite light to a specific location to the outside world. By rasteringthe laser beam using the MEMS mirror a pixel in two dimensions can beformed to create a pattern or image.

According to an embodiment, the present invention includes a housinghaving an aperture and an input interface for receiving one or moresignals such as frames of images. The dynamic light system also includesa processing module. In one embodiment, the processing module iselectrically coupled to an ASIC for driving the laser diode and the MEMSscanning mirrors.

In one embodiment, a laser driver module is provided. Among otherthings, the laser driver module is adapted to adjust the amount of powerto be provided to the laser diode. For example, the laser driver modulegenerates a drive current based one or more pixels from the one or moresignals such as frames of images, the drive currents being adapted todrive a laser diode. In a specific embodiment, the laser driver moduleis configured to generate pulse-modulated signal at a frequency range ofabout 50 to 300 MHz.

According to an embodiment, the present invention provides a dynamiclaser-based light source or light projection apparatus including ahousing having an aperture. The apparatus can include an input interfacefor receiving a signal to activate the dynamic feature of the lightsource. The apparatus can include a video or signal processing module.Additionally, the apparatus includes a light source based on a lasersource. The laser source includes one or more of a violet laser diode orblue laser diode. The dynamic light feature output comprised from aphosphor emission excited by the output beam of a laser diode, or acombination of a laser diode and a phosphor member. The violet or bluelaser diode is fabricated on a polar, nonpolar, or semipolar orientedGa-containing substrate. The apparatus can include a laser driver modulecoupled to the laser source. The apparatus can include a digital lightprocessing (DLP) chip comprising a digital mirror device. The digitalmirror device including a plurality of mirrors, each of the mirrorscorresponding to one or more pixels of the one or more frames of images.The apparatus includes a power source electrically coupled to the lasersource and the digital light processing chip.

The apparatus can include a laser driver module coupled to the lasersource. The apparatus includes an optical member provided withinproximity of the laser source, the optical member being adapted todirect the laser beam to the digital light processing chip. Theapparatus includes a power source electrically coupled to the lasersource and the digital light processing chip. In one embodiment, thedynamic properties of the light source may be initiated by the user ofthe apparatus. For example, the user may activate a switch, dial,joystick, or trigger to modify the light output from a static to adynamic mode, from one dynamic mode to a different dynamic mode, or fromone static mode to a different static mode.

In a specific embodiment of the present invention including a dynamiclight source, the dynamic feature is activated by a feedback loopincluding a sensor. Such sensors may be selected from, but not limitedto a microphone, geophone, hydrophone, a chemical sensor such as ahydrogen sensor, CO2 sensor, or electronic nose sensor, flow sensor,water meter, gas meter, Geiger counter, altimeter, airspeed sensor,speed sensor, range finder, piezoelectric sensor, gyroscope, inertialsensor, accelerometer, MEMS sensor, Hall effect sensor, metal detector,voltage detector, photoelectric sensor, photodetector, photoresistor,pressure sensor, strain gauge, thermistor, thermocouple, pyrometer,temperature gauge, motion detector, passive infrared sensor, Dopplersensor, biosensor, capacitance sensor, video sensor, transducer, imagesensor, infrared sensor, SONAR, LIDAR, or others.

In one example of a dynamic light feature including a feedback loop witha sensor a motion sensor is included. The dynamic light source isconfigured to illuminate a location where the motion is detected bysensing the spatial of position of the motion and steering the outputbeam to that location. In another example of a dynamic light featureincluding a feedback loop with a sensor an accelerometer is included.The accelerometer is configured to anticipate where the laser lightsource apparatus is moving toward and steer the output beam to thatlocation even before the user of the apparatus can move the light sourceto be pointing at the desired location. Of course, these are merelyexamples of implementations of dynamic light sources with feedback loopsincluding sensors. There can be many other implementations of thisinvention concept that includes combining dynamic light sources withsensors.

In certain embodiments, the integrated white light source apparatus, thesource is operable in an environment comprising at least 150,000 ppmoxygen gas.

In certain embodiments, the integrated white light source apparatus, thesupport member comprises a material selected from copper, coppertungsten, aluminum, silicon, and a combination of any of the foregoing.

In certain embodiments, the integrated white light source apparatuscomprises a microchannel cooler thermally coupled to the support member.

In certain embodiments, the integrated white light source apparatuscomprises a heat heat-sink thermally coupled to the common supportmember. In one example the heat sink has fins or a measure for increasedsurface area.

In certain embodiments, the integrated white light source apparatuscomprises a heat spreader coupled between the common support member andthe heat sink.

In certain embodiments, the integrated white light source apparatus, anoptical coupler comprises one or more optical fibers.

In certain embodiments of the integrated white light source apparatus,the output beam is geometrically configured to optimize an interactionwith a phosphor material.

In certain embodiments of the integrated white light source apparatus,the white light source is configured in a package. In one example, thepackage is hermetically sealed.

In certain embodiments of the integrated white light source apparatus,the white light source is configured in a package such a flatpackage(s), surface mount packages such as SMDs, TO9 Can, TO56 Can, TO-5can, TO-46 can, CS-Mount, G-Mount, C-Mount, micro-channel cooledpackage(s), and others.

In certain embodiments of the integrated white light source apparatus,the emitted white light is collimated using a reflector or lens.

What is claimed is:
 1. An integrated white light source for a vehicle orother application using a beam of light, comprising: a laser diodedevice comprising a gallium and nitrogen containing material andconfigured as an excitation source; a phosphor member configured as awavelength converter and an emitter, the phosphor member coupled to thelaser diode device; a common support member configured to support thelaser diode device and the phosphor member, a heat sink coupled to thecommon support member, the common support member configured to transportthermal energy from the laser diode device and the phosphor member tothe heat sink; a submount member configured with the laser diode deviceto form a chip on a submount structure; an output facet configured tothe laser diode device to output a laser beam of electromagneticradiation from the output facet; the electromagnetic radiation beingselected from a violet or a blue emission with a first wavelengthranging from 400 nm to 485 nm, the output beam being characterized by awavelength range, a spectral width, a power, and a spatialconfiguration: a free space, within a vicinity of the common supportmember, with a non-guided characteristic capable of transmitting thelaser beam from the laser diode device to a beam spot on an excitationsurface of the phosphor member; and the laser beam of the laser diodedevice being optically coupled to the phosphor member; an angle ofincidence configured between the laser beam and the excitation surfaceof the phosphor member so that the laser beam has an off-normalincidence to the excitation surface of the phosphor member, the beamspot on the excitation surface being configured for a certaingeometrical size and shape based on the angle of incidence and adistance between the output facet of the laser diode device and theexcitation surface of the phosphor member, the phosphor member beingconfigured to convert at least a fraction of the electromagneticradiation in the laser beam with a first wavelength to a secondwavelength that is longer than the first wavelength; a reflective modecharacterizing the phosphor member such that the laser beam is incidenton the excitation surface of the phosphor member; a white light emittedfrom the excitation surface of the phosphor member, the white lightemission being comprised of a mixture of wavelengths characterized by atleast the second wavelength from the phosphor member; a transparent lidmember coupled to the common support member, the transparent lid memberhas a curved hemispherical shape; and a form factor characterizing theintegrated white light source, the form factor having a length, a width,and a height dimension.
 2. The integrated white light source of claim 1,wherein the common support member is configured from the submount membersuch that the phosphor member and the laser diode device share thesubmount member and comprise the chip and the phosphor member on thesubmount structure.
 3. The integrated white light source of claim 2,wherein the phosphor member is coupled to the submount member using anintermediate submount or material.
 4. The integrated white light sourceof claim 1, wherein the laser diode device is characterized by a firstblue wavelength in the range of 425 nm to 480 nm, the second wavelengthfrom the phosphor member comprises a yellow wavelength range, andwherein the white light emission is comprised of the first bluewavelength and the second yellow wavelength range.
 5. The integratedwhite light source of claim 4, wherein the phosphor member is comprisedof a ceramic yttrium aluminum garnet (YAG) doped with Ce or a singlecrystal YAG doped with Ce; and wherein the phosphor member has anoptical conversion efficiency of at least 50 lumen per optical watt. 6.The integrated white light source of claim 1, wherein the phosphormember comprises a first phosphor component and a second phosphorcomponent, the first phosphor component configured to emit the secondwavelength and the second phosphor component configured to emit a thirdwavelength.
 7. The integrated white light source of claim 6, wherein thelaser beam is comprised of the violet emission, the first phosphorcomponent is characterized by a blue emission having the secondwavelength, and the second phosphor component is characterized by ayellow emission having the third wavelength, and wherein the white lightemission is comprised of at least the second wavelength and the thirdwavelength.
 8. The integrated white light source of claim 6, wherein thelaser beam is comprised of the blue emission, the first phosphorcomponent is characterized by a green emission having the secondwavelength, and the second phosphor component is characterized by a redemission having the third wavelength, and wherein the white lightemission is comprised of at least the first wavelength, the secondwavelength, and the third wavelength.
 9. The integrated white lightsource of claim 1, further comprising at least one of or a combinationof a spectral filter, a spatial filter, an angular filter, a reflector,or a phosphor shaping to improve efficiency of the integrated whitelight source by increasing an amount of useful white light exiting theat least one emission surface of the phosphor member; wherein thespectral filter, the spatial filter, the angular filter, the reflector,or the phosphor shaping are formed from a coating material on one ormore surfaces of the phosphor member, a sheet material applied to one ormore surfaces of the phosphor member, or positioning an additionalelement adjacent to the phosphor member.
 10. The integrated white lightsource of claim 1, further comprising at least one of or a combinationof a passive safety feature including a beam dump configured to absorblaser light and an active safety feature having an integrated photodiodeconfigured to turn the laser diode device off when a change in signal issensed.
 11. The integrated white light source of claim 1, wherein thelaser beam is configured for a certain geometrical shape and size uponincidence on the phosphor member; and wherein the laser beam isconfigured using an integrated free-space optic to collimate and/orshape the laser beam.
 12. The integrated white light source of claim 1,wherein the height dimension is less than 25 mm and greater than 1 mm.13. The integrated white light source of claim 1, wherein the commonsupport member comprises a material selected from copper, coppertungsten, aluminum, silicon, silicon carbide, aluminum nitride, diamond,and a combination of any of the foregoing.
 14. The integrated whitelight source of claim 1, wherein the submount member comprises amaterial selected from silicon carbide, aluminum nitride, berylliumoxide, composite diamond, diamond, and a combination of any of theforegoing.
 15. The integrated white light source of claim 1, wherein thesubmount member and the common support member are characterized by athermal conductivity of at least 200 W/(m·K).
 16. The integrated whitelight source of claim 1, wherein the white light emission is comprisedof at least 50 lumens.
 17. The integrated white light source of claim 1,wherein the integrated white light source is configured in a package;wherein the package is characterized by a sealing selected from an openenvironment sealing, an environmental sealing, or a hermetic sealing.18. The integrated white light source of claim 17, wherein the packageis selected from a can type, a flat package type, a surface mount type,a butterfly type, a C-mount type, or a Q-mount type.
 19. The integratedwhite light source of claim 1, wherein the white light emission iscollimated using optics to project the white light emission into a beamshape; and wherein the optics are comprised of a reflector or a lens.20. An integrated white light source for a vehicle or other applicationusing a beam of light, comprising: a laser diode device comprising agallium and nitrogen containing material, and configured as anexcitation source; a phosphor member comprised of yttrium aluminumgarnet (YAG) and configured as a wavelength converter and an emitter,the phosphor member coupled to the laser diode device; a common supportmember configured to support the laser diode device and the phosphormember, the common support member being configured to transport thermalenergy from the laser diode device and the phosphor member; a heat sinkcoupled to the common support member and configured to receive thethermal energy from the laser diode device and the phosphor member; asubmount configured to the laser diode device to form a chip on thesubmount; an output facet configured on the laser diode device to outputa laser beam of electromagnetic radiation from the output facet, theelectromagnetic radiation being selected from a violet or a blueemission with a first wavelength ranging from 400 nm to 485 nm, thelaser beam being characterized by a wavelength range, a spectral width,a power, and a spatial configuration: a free space, within a vicinity ofthe common support member, with a non-guided characteristic capable oftransmitting the laser beam from the laser diode device to the phosphormember, the laser beam of the laser diode device being optically coupledto the phosphor member; an angle of incidence configured between thelaser beam and the phosphor member, the phosphor member configured toconvert at least a fraction of the electromagnetic radiation in thelaser beam with a first wavelength to a second wavelength that is longerthan the first wavelength; a reflective mode characterizing the phosphormember, the laser beam being incident on a first primary surface of thephosphor member and a white light being emitted from at least aninteraction of the electromagnetic radiation with the first primarysurface, the white light emission comprising of a mixture of wavelengthscharacterized by at least the second wavelength from the phosphormember; a transparent lid member coupled to the common support member,the transparent lid member has a curved hemispherical shape; and a formfactor characterizing the integrated white light source and having alength, a width, and a height dimension.
 21. The integrated white lightsource of claim 20, wherein the common support member comprises thesubmount such that the phosphor member and the laser diode device areprovided on the submount and comprise the chip and the phosphor memberon the submount.
 22. The integrated white light source of claim 20,further comprising an intermediate submount or material to attach thephosphor member to the submount.
 23. The integrated white light sourceof claim 20, wherein the angle of incidence between the laser beam andthe phosphor member is comprised of an incidence angle with respect to afast-axis of the laser beam and an incidence angle with respect to aslow-axis of the laser beam; wherein at least one of the incidence anglewith respect to the fast axis or the incidence angle with respect to theslow axis is an off-normal angle relative to a surface of the phosphormember ranging between 0 degrees and 89 degrees.
 24. The integratedwhite light source of claim 20, wherein the laser diode device has afirst blue wavelength in the range of 425 nm to 480 nm, the secondwavelength from the phosphor member is a yellow wavelength range, andwherein the white light emission is comprised of the first bluewavelength and the yellow wavelength range.
 25. The integrated whitelight source of claim 24, wherein the phosphor member is comprised of aceramic YAG doped with Ce or a single crystal YAG doped with Ce; andwherein the phosphor member has an optical conversion efficiency of atleast 50 lumen per optical watt.
 26. The integrated white light sourceof claim 20, wherein the phosphor member comprises a first phosphorcomponent and a second phosphor component, the first phosphor componentconfigured to emit the second wavelength and the second phosphor memberconfigured to emit a third component.
 27. The integrated white lightsource of claim 26, wherein the laser beam is comprised of the violetemission, the first phosphor component is characterized by a blueemission having the second wavelength, and the second phosphor componentis characterized by a yellow emission having the third wavelength, andwherein the white light emission is comprised of at least the secondwavelength and the third wavelength; or wherein the laser beam iscomprised of the blue emission, the first phosphor component ischaracterized by a green emission having the second wavelength, and thesecond phosphor component is characterized by a red emission having thethird wavelength, and wherein the white light emission is comprised ofat least the first wavelength, the second wavelength, and the thirdwavelength.
 28. The integrated white light source of claim 20, furthercomprising at least one of or a combination of a reflector material, aspectral filter, a spatial filter, an angular filter, a phosphorroughening, or a phosphor shaping to improve efficiency of theintegrated white light source by increasing an amount of useful whitelight exiting the at least one emission surface of the phosphor member.29. The integrated white light source of claim 20, further comprising atleast one of or a combination of a passive safety feature including abeam dump configured to absorb laser light and an active safety featurehaving an integrated photodiode configured to turn the laser diodedevice off when a change in signal is sensed.
 30. The integrated whitelight source of claim 20, wherein the laser beam is configured for acertain geometrical shape and size upon incidence on the phosphormember; and wherein the laser beam is configured using an integratedfree-space optic to collimate and/or shape the laser beam.
 31. Theintegrated white light source of claim 20, wherein the laser beam isconfigured for a certain geometrical size and shape upon incidence onthe phosphor member; and wherein the laser beam is configured using atleast one of or a combination of selecting a designed distance betweenthe output facet and the phosphor member, a tilting of the phosphormember with respect to the laser beam, and a tilting of the laser diodedevice with respect to the phosphor member.
 32. The integrated whitelight source of claim 20, wherein the height dimension is less than 25mm and greater than 1 mm.
 33. The integrated white light source of claim20, wherein the common support member comprises a material selected fromcopper, copper tungsten, aluminum, silicon, silicon carbide, aluminumnitride, diamond, and a combination of any of the foregoing.
 34. Theintegrated white light source of claim 20, wherein the submountcomprises a material selected from silicon carbide, aluminum nitride,beryllium oxide, composite diamond, diamond, and a combination of any ofthe foregoing.
 35. The integrated white light source of claim 20,wherein the submount and the common support member are characterized bya thermal conductivity of at least 200 W/(m·K).
 36. The integrated whitelight source of claim 20, wherein the white light emission is comprisedof at least 50 lumens.
 37. The integrated white light source of claim20, wherein the integrated white light source is configured in apackage; wherein the package is characterized by a sealing selected froman open environment sealing, an environmental sealing, or a hermeticsealing.
 38. The integrated white light source of claim 37, wherein thepackage is selected from a can type, a flat package type, a surfacemount type, a butterfly type, a C-mount type, or a Q-mount type.
 39. Theintegrated white light source of claim 20, wherein the white lightemission is collimated using optics to project the white light emissioninto a beam shape; and wherein the optics are comprised of a reflectoror a lens.
 40. An integrated white light source for a vehicle or otherapplication using a beam of light, comprising: a laser diode device,comprising a gallium and a nitrogen containing material, configured asan excitation source; a phosphor member configured as a wavelengthconverter and an emitter, the phosphor member coupled to the laser diodedevice; a common support member configured to support the laser diodedevice and the phosphor member, the common support member beingconfigured to transport thermal energy from the laser diode device andthe phosphor member; a heat sink coupled to the common support member toreceive the transported thermal energy, the laser diode device beingconfigured on a submount to form a chip on the submount, an output facetconfigured on the laser diode device to output a laser beam ofelectromagnetic radiation from the output facet; the electromagneticradiation being selected from a violet or a blue emission with a firstwavelength ranging from 390 nm to 485 nm, the laser beam beingcharacterized by a wavelength range, a spectral width, a power, and aspatial configuration; a free space, within a vicinity of the commonsupport member, with a non-guided characteristic capable of transmittingthe laser beam from the laser diode device to the phosphor member, thelaser beam of the laser diode device optically coupled to the phosphormember; an angle of incidence configured between the laser beam and thephosphor member, the phosphor member being configured to convert atleast a fraction of the electromagnetic radiation in the laser beam witha first wavelength to a second wavelength that is longer than the firstwavelength; a phosphor material comprising at least a polycrystallinematerial or single crystal YAG:Ce material characterizing the phosphormember, the phosphor material comprising a 3-dimensional geometry withthe laser beam being directed from the output facet directly to anexcitation surface of the phosphor material; a white light emissionderived from a plurality of sides of the 3-dimensional geometry, thewhite light emission being comprised of a mixture of wavelengthscharacterized by at least the second wavelength from the phosphormember; a transparent lid member coupled to the common support member,the transparent lid member has a curved hemispherical shape; and a formfactor characterizing the integrated white light source, and having alength, a width, and a height dimension.
 41. The integrated white lightsource of claim 40, wherein the phosphor member is configured from aspherical shape, a hemispherical shape, an aspherical shape, a cubeshape, or a cylinder shape.